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General
Electromigration in VLSI of thin film interconnects
K. N. Tu
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On a piece of silicon chip of the size of a fingernail, we can make hundreds of millions of transistors. The chip is the building block of modern microelectronic devices and computers. To function together, the transistors must be interconnected by ultra-fine aluminum or copper thin film wires having a diameter of less than one hundredth of our hair. These wires are called interconnects and carry a very high electric current density during device operation. The high current density can cause atomic displacement in the wire and lead to void (open) and extrusion (short) formation. The displacement is called electromigration and it is the most serious and persistent reliability problem of microelectronic devices and computers. The interconnects are 3-dimensional and are insulated by ultra-thin dielectric. The insulation induces thermal stress between the wire and the dielectric. The 3-dimentional structure induces current crowding when the interconnect turns, which enhances electromigration. In this proceedings paper, we review briefly what is new about electromigration in Cu interconnects.
Thin films in silicon carbide semiconductor devices
Mikael Ostling,
Sang-Mo Koo,
Sang-Kwon Lee,
et al.
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Silicon carbide (SiC) semiconductor devices have been established during the last decade as very useful high power, high speed and high temperature devices because of their inherent outstanding semiconductor materials properties. Due to its large band gap, SiC possesses a very high breakdown field and low intrinsic carrier concentration, which accordingly makes high voltage and high temperature operation possible. SiC is also suitable for high frequency device applications, because of the high saturation drift velocity and low permittivity. Thin film technology for various functions in the devices has been heavily researched. Suitable thin film technologies for Ohmic and low-resistive contact formation, passivation and new functionality utilizing ferroelectric materials have been developed. In ferroelectrics, the spontaneous polarization can be switched by an externally applied electric field, and thus are attractive for non-volatile memory and sensor applications. A novel integration of Junction-MOSFETs (JMOSFETs) and Nonvolatile FETs (NVFETs) on a single 4H-SiC substrate is realized. SiC JMOSFET controls the drain current effectively from the buried junction gate thereby allowing for a constant current level at elevated temperatures. SiC NVFET has similar functions with non-volatile memory capability due to ferroelectric gate stack, which operated up to 300°C with memory function retained up to 200°C.
Making ferromagnetic semiconductors out of III-V nitride semiconductors
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Transition metal doped III-V nitrides including Mn- or Cr-doped GaN and InN are grown by molecular beam epitaxy (MBE). Structural, electronic and magnetic properties have been investigated. Cr-doped GaN shows room temperature ferromagnetism. Bulk sensitive high-energy x-ray photoemission spectroscopy is performed at SPring-8 to elucidate electronic structure of Cr-doped GaN. It is found that the doped Cr contributes to form gap states, which pin the Fermi level. The gap state is attributed to Ga 4s originated state caused by strong hybridization between Cr 3d and band electrons of host GaN. InN-based system were grown by low temperature MBE. Highly Mn-doped InN shows spin-glass states. Anti-ferromagnetic interaction between Mn ions in InN was suggested. Contrary to the Mn-doped InN, Cr-doped InN shows ferromagnetic property at room temperature.
Thin Film Physics
Fabrication of magnetic nanostructures and devices by AFM nanolithography technique
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Magnetic nanostructures and devices were fabricated by a combination of conventionally photo or electron beam lithography and atomic force microscopy (AFM) lithography. Ni- and Co(Fe)-based nanostructures of oxide were successfully fabricated by applying a negative pulse voltage to the AFM cantilever. Both of height and width of the oxide nanostructures were controlled by changing the applied bias voltage to the cantilever. Ni/Ni-oxide planar-type magnetic tunnel junctions were fabricated by this technique and the current-voltage curve exhibited a diode characteristic. It was also found that magnetic domain structures were controlled by the AFM nano-oxidation. This nanolithography is a promising technique for fabricating magnetic nanostructures for quantum devices and new functional materials.
The second law of thermodynamics for advanced thin films
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In recent years, many advanced thin films had been successfully prepared under activated nonequilibrium conditions. However, based on classical thermodynamics the low-pressure diamond synthesis had been regarded as violating the second law of thermodynamics. After removing the “bug” hidden in classical concepts of thermodynamics, a new field of modern thermodynamics, nonequilibrium nondissipative thermodynamics, emerges in the equality part of the second law. The new progress in the second law of thermodynamics provides a firm theoretical base of calculating nonequilibrium phase diagrams for advanced thin films. Thermodynamic coupling in these systems has been discussed from both sides in physics and in mathematics. Our coupling model for diamond films growth was cited in the Journal Nature with a nice comment.
MBE growth and properties of InN and InN-based diluted magnetic semiconductors
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InN films were grown by N2 plasma-assisted molecular beam epitaxy (MBE) on Al2O3 substrates. The films were characterized by reflection high-energy electron diffraction, atomic force microscope, x-ray diffraction methods and Raman spectrum, indicating high crystalline quality of the films. The optical absorption and photoluminescence measurement show the band-gap energy of InN films was located about 1.0-1.1 eV.
InN-based diluted magnetic semiconductor (DMS) In1-xMnxN and In1-xCrxN films were prepared by N2 plasma-assisted MBE at low temperature. Microstructure characterization indicates Mn was homogeneously incorporated into InN up to 4% and 10% respectively at 300°C and 200°C, while Cr was incorporated up to 4% at 300°C. A paramagnetic to spin-glass transition was observed at 3 K in In0.9Mn0.1N films grown at 200°C. Room temperature ferromagnetism was observed for the homogeneous In0.98Cr0.02N films.
Formation and characteristics of quantum dots of wide-bandgap II-VI semiconductor
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CdSe and ZnCdSe quantum dots (QDs) were grown under Stranski-Krastanow (S-K) mode by low-pressure metalorganic chemical vapor deposition (LP-MOCVD). The formation process of CdSe QDs below critical thickness was observed by atomic force microscopy (AFM). The formation mechanism of CdSe QDs below the critical thickness was due to the effect of surface diffusion and strain release. ZnCdSe QDs were grown based on the calculated critical thickness. Two kinds of variations in the ZnCdSe QDs appeared over time, the Ostwald ripening process and dot formation process. ZnSeS dots were grown under Volmer-Weber (V-W) mode. With increasing the growth duration, the size of dots becomes larger and the density decreases, which is explained by virtue of the surface free energy.
The characteristic criterion of the growth of metallic films from discontinuous to continuous
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A characteristic criterion of the growth of metallic films from discontinuous to continuous has been proposed. That is, when the electric conductivity σ of thin metallic film equals to 63.2% of the electric conductivity σ of the infinitely thick metallic film, the growth of metallic films come into continuous film. The corresponding equivalent thickness d0 of the characteristic criterion can be thought of as the characteristic thickness of the growth of metal films from discontinuous to continuous. According this characteristic criterion, the characteristic thicknesses of Co films and Cu films have been given. The topography images of Co and Cu films have been observed using atomic force microscopy.
Ballistic emission spectroscopy and imaging of a buried metal-organic interface
N. Chandrasekhar,
Cedric Troadec,
Linda Kunardi
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Metal organic interfaces have been under intensive scientific investigation over the past few years with the objective of improving devices based on organic materials. In this study, we report the first results on spectroscopy and imaging of a buried metal-organic interface using ballistic electron emission microscopy (BEEM). Unlike photoexcitation-based experiments, which typically average over large interfacial areas, BEEM enables direct observation of local interface band structure with nanometer resolution. The interface of silver (Ag) - polyparaphenylene (PPP, a blue emitter with high photoluminescence efficiency) is investigated. Multiple injection barriers and spatial non-uniformity of carrier injection are observed. Possible causes for these features will be discussed. The BEEM current images are found to correlate marginally with the surface topography of the silver film.
Comparative study on Al-doped ZnO films sputtered with ceramics and metal targets
Le-Xi Shao,
Xiao-Ping Liu,
Huey-Liang Hwang
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ZnO:Al thin films were deposited on glass and Si wafer substrates respectively by sputtering ceramics ZnO:Al2O3 and reactively sputtering metal Zn:Al targets for the purpose to find a suitable method for improving both conductivity and transparency of the film. The properties of the deposited films were investigated to determine the differences between the sputtered and reactive sputtered samples by using scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray analysis (EDX), UV-VIS spectrometer and electrical measurements. The results show that the films sputtered reactively with metal have a very high crystalline quality and transmittance in the visible light wave range, while the films sputtered with ceramics can obtain good conductivity and its crystalline structural quality can be improved largely by introducing oxygen into the deposition system.
Monte Carlo study of Kerr effect in NixSi02(1-x) granular films
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Monte Carlo method has been applied to simulate the hysteresis loops from VSM and MOKE measurement for NixSiO2(1-x) granular films. The simulated results reveal that: (1) The calculated Kerr loops are in good agreement with the experimental data. (2) The anisotropy constant decreases with the increasing packing fraction of Ni clusters; (3) Generally, the difference between the hysteresis loops obtained from VSM and Kerr effect respectively always exists for the finite incident angle. It increases with increasing incident angle. It for strong ferromagnetic films is smaller than those for weak or mixed magnetic films.
Size and step effects of hysteresis in mixed magnetic films
Zhenzhen Weng,
Zhi-gao Huang
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Size effect of the coercivity and step effect in the ferromagnetic/antiferromagnetic (FM/AFM) mixed magnetic films are studied by a micromagnetism and Monte Carlo methods. Step effect is found in the simulation, which can be explained by the simple mean field theory. The calculated results indicate that it is attributed to the different response of the clusters with different size and different diluted ratio of antiferromagnetic atom on the external field, which is explained by the simple mean field theory well. The dependence of the diluted ratio of ferromagnetic atom x on the coercivity Hc is also simulated. The simulated results explain the experimental facts for the mixed magnetic films well.
Effects of the next-nearest-neighbor interaction on the phase transition of magnetic multilayers
Liqin Jiang,
Qian Feng,
Zhi-gao Huang
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Based on Ising model, the effects of nearest and next-nearest neighbor interactions on the magnetic properties of films with BCC structure have been studied by an improved 4×4 transfer matrix method. The dependence of the phase transition temperature TCon both the ratio of surface coupling to bulk one Js/JBand the next-nearest coupling to nearest one b and the size of the system are studied. It is found that there exists a multicritical value Js/JB (JC) at which the phase transition temperature TCat the surface is the same as that in the body. The dependence of JCon the value of bfor different number of surface layers is also studied. The calculated results are well consistent with the experimental facts.
Mesostructure of Fe-based ribbon influenced by inner stress
Yun Zhang Fang,
W. H. Wu,
J. J. Zheng,
et al.
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The mesostructure of Fe-based (Fe73.5Cu1Nb3Si13.5B9)nanocrystalline ribbon was observed by investigation of the section samples and the molted samples with atomic force microscopy (AFM). The section of the Fe-based crystalline ribbon can be divided into five areas. An apparent mesostructural difference was found in the different areas of the ribbon crystallized after annealing. In RFA, the coarse grains gathering in longitudinal arrangement, while in FFA the fine grains gathering arranged transversely dominates. The size of crystalline grain increases from about 10 nm to about 300 nm with the area gradating from the free surface to the rolled surface. The main reason for such mesostructural difference could be due to the different residual inner stress in the different areas of the amorphous ribbon.
Ab initio study of electronic properties of CoSi2 and NiSi2 in the fluorite structure
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The lattice structure and electronic properties of perfect CoSi2 and NiSi2 have calculated using an ab initio plane-wave ultrasoft pseudopotential method based on the generalized gradient approximations (GGA). Special attention is paid to the formation energies of the vacancy, which largely depend on the atomic chemical potentials of Si and metal atom: in Si-rich limit, the formation energies of Si and Co vacancies are 2.39 eV and 0.56 eV whilst those are 1.53 eV and 2.29 eV in Co-rich limit in CoSi2, respectively. For NiSi2, the formation energies of Si and Ni vacancies are 0.56 eV and 1.25 eV in Si-rich limit and those are 0.04 eV and 2.3 eV in Ni-rich limit.
Formation of GaAs hollow above InAs quantum dots
Hua Han Zhan,
Jun Yong Kang
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GaAs hollow nanostructure is constructed above low-temperature (250°C) InAs quantum dots after a thin GaAs layer capping at 480°C. The hollows mostly disappeared after the high temperature annealing at 580°C. The formation mechanism is simply discussed.
Improve the charge stability of SiO2 films by plasma treatment and ion implantation
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The plasma surface treatment and ion implantation are utilized to improve the stability of charge storage of the SiO2 film electret. The effects are obviously different when the different kinds of plasma are used, and when the ions with different energy and dose implanted into the SiO2 film. To the plasma treatment, the best effect is obtained with argon plasma. After argon plasma treatment with the arcing at 700V and 15 minutes for the SiO2 film electret, its charge storage has a similar stability as one after the chemical surface modification. To the ion implantation method, the remanent surface potential is 95%of primary one after ion implantation by Ar+ with a energy of 150KeV and a dose of 2E11/cm2. The experimental results show that argon plasma treatment and Ar+ implantation change the hydrophilicity of the surface of SiO2 film and prevent the electret charge from leaking, which is owning to the increase of the surface conductance by the vapor adherence on the surface. In addition, the plasma bombardment and ion implantation induce traps into the near-surface, which make the trapped charge stored stable.
Photovoltaic feature of boron-doped nanocrystalline carbon films on silicon
Z. Q. Ma,
Q. Zhang
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Boron-doped diamond-like carbon (B-DLC) thin films were deposited on n-type silicon (100) substrates by arc-discharge plasma chemical vapor deposition (arc-PCVD) technique, followed by a deposition of TiNx (0.8 < x < 1.1) mark on top of the carbon films to form heterojunction devices. The crystallinity of the carbon film was confirmed to be a mixing of sp3/sp2 coordination with nanocrystalline diamond grains embedded in the amorphous network. The performance of TiNx / p-C (B) / n-Si / AuSb heterojunction cells has been evaluated under dark I-V rectifying curve and I-V working curve with a proper illumination. At higher boron content the films exhibited a high internal conductivity and an overall phase-related character. The TiNx exhibited an excellent ohmic contact behavior as a metallic electrode of the devices.
A novel application of the solid electrolyte thin film for preparing copper nanowires
Shuo Shi,
Jia-Lin Sun,
Guo-Sheng Zhang,
et al.
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We report a novel application of the solid electrolyte K-Cu-I thin film for preparing copper nanowires. The K-Cu-I film was prepared by depositing a mixture of KI and CuI powders on a heated glass substrate in vacuum and had a copper ion conductivity of 1.5x10-3Ω-1cm-1 at 540K. At 540K, being applied a direct current (DC) electric field of 1.0x104 V/m, the copper ions migrated toward cathode through the K-Cu-I film and congregated to form nanowires at the edge of the cathode. The copper nanowires were about 40~100nm in diameter and several micrometers in length.
Energy resolution in x-ray detecting microstrip gas chamber fabricated on CVD diamond films
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The valuable properties of CVD diamond films used as micro-strip gas chamber (MSGC) substrate are presented and a gas detector with an area of 20x20mm2 was fabricated on a CVD diamond film whose resistivity ranges between 1010 and 1011Ω-cm. We systematically report the energy spectra generated by a 5.9keV55Fe X-ray source. The effects of high potential on the energy resolution are investigated and discussed in detail. A better energy resolution about 12.2% is obtained when MSGC filling with an argon+10%CH4 gas mixture operated at a drift potential of -1100V and a cathode voltage of -650V.
Deposition and characterizations of GeCN thin films
Fuchun Xu,
Jun Yong Kang
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Germanium-carbon-nitride (GeCN) thin films were deposited on different substrates by reactive magnetic co-sputtering. As-deposited films were characterized with respect to composition, microstructure, and optical relection. The results show that quality of the film deposited on ZrN substrate is better and the band gaps is about 3.4 eV.
Theoretical analysis of atom focusing for nanostructure fabrication
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The two-level atom focusing in a Gaussian standing wave laser field was analyzed from the perspective of both classical mechanics and wave mechanics. The effects of source imperfection such as velocity spread and beam spread on atom focusing were analyzed by numerically integrating the classical equation of atomic motion. The ideal focal plane can be easily determined by the variation of atomic density at the minimal potential of the standing wave laser field as a function of traveling distance. In the absence of source imperfection, the contribution of diffractive aberration originating from the wave nature of the atom to broadening of feature width is larger than that of spherical aberration. Several methods for improving atom lithography experiments were presented.
MBE growth and magnetoresistance properties of PrSrMnO3 films on NdGaO3(100) substrate
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Pr1-xSrxMnO3 (100) thin films were prepared on NdGaO3 (100) substrate by RF-plasma-assisted molecular beam epitaxy method. The films were characterized by reflection high-energy electron diffraction, atomic force microscope and x-ray diffraction methods, indicating perfect surface smoothness and high crystalline quality. Large low field magnetoresistance effects with strong anisotropic properties of the non-stoichiometric (Pr1-xSrx)yMnO3 films have been observed. These results may be connected with the large A-site deficient in the films.
Thickness effects on microwave properties and ferromagnetic resonance of Fe-Co-B magnetic thin films
Yi Yang,
Wei Tian,
Gang Lu,
et al.
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In order to apply Fe-Co-B thin films for high-frequency magnetic devices, the thickness effects on the magnetic properties and microwave properties of these films have been studied. The complex permeability of these thin films has been measured at the frequency of 2GHz with cavity. The real part of the permeability μ/ of the thin films increases with the decease of the thickness of the thin films because the decrease of the thickness of the thin films leads to the increase of the natural resonance frequency. The imaginary part of the permeability μ// of the thin films exhibits a minimal value at 150nm thickness, which is due to the simultaneous effect of the natural resonance and eddy current effect. The FMR line width broadening can be observed with the increase of the thickness of the thin films from the FMR investigation, which supports the research results above.
Calculation of temperature field of CO2 laser conditioning of fused silica
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We calculate the transient and steady state temperature field of CO2 laser conditioning of fused silica using thermal transporting model. We find that surface temperature at the beam center grows rapidly at the initial heating stage both for the linear thermal transport and nonlinear heat transport, then grows very slowly approaching the stationary value. The axial thermal gradients of nonlinear thermal transport, accounting for the increased thermal conductivity at high temperature, are more smooth than those of the linear case.
Efficient field emission from porous silicon
Yongsheng Zhang,
Ke Yu,
Laiqiang Luo,
et al.
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Patterned porous silicon (PS) films were fabricated based on hydrogen ion implantation technique and typical electrochemical anodic etching method. The surface morphology and characteristics of the films were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and atomic force microscopy (AFM). The efficient field emission with low turn-on field of about 3.5V/μm at current density of 0.1μA/cm2 was obtained. The emission current density from the PS films reached 1mA/cm2 under a applied field of about 12.5V/μm. The experimental results demonstrate that the PS films have great potential applications for flat panel displays.
Effect of high-energy ball milling on morphology and field emission properties of multi-walled carbon nanotubes
Laiqiang Luo,
Ke Yu,
Yongsheng Zhang,
et al.
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The effects of grinding for different time in a vibrating mill with the mixture of Fe powder and multi-walled carbon nanotubes (MWNTs) were studied. The morphology and structure of as-ground MWNTs were carried out by X-ray diffraction (XRD) and High-resolution transmission electronic microscopy (HRTEM). The results showed that some closed ends of MWNTs were broken while ground for 8 hours, and the rate of broken ends increased with grinding time. The Field emission measurements demonstrated that the turn-on field of the sample decreased from 4.0 to 2.6 V/μm after grinding.
Thin Film Materials
Piezoelectric PZT thin films derived by sol-gel techniques
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In this report, piezoelectric Pb(ZrxTi1-x)O3 (PZT) thin films have been prepared onto platinized silicon and stainless steel substrates (SS) respectively, by using the sol-gel spin-on techniques and rapid thermal annealing (RTA) process. (i) Near 4 μm (100) oriented PZT thin films were prepared onto (111)Pt/Ti/SiO2/Si. The dielectric constant and remnant polarization achieved 1658 and 35 μC/cm2 respectively. Zr-rich PZT thin films had higher dielectric constant. The as-prepared PZT thin films were observed to have spontaneous piezoelectric responses, which was prominent in the relatively thinner films. (ii) PZT thin films were successfully deposited onto SS substrates by using a thin template of PbTiO3 layer. The annealing temperature of PZT was decreased to 550°C. No second phase was detected to the limit of X-ray diffractmeter. The remnant polarization and piezoelectric d31 constant were determined to be 35 μC/cm2 and -76 pC/N, respectively. (iii) The origin of the self-poling effect was conjectured to the formation of an internal bias field in PZT thin films. The shift of Curie temperature Tc of PZT thin films was discussed on the base of two-dimensional compressive and tensile stresses introduced by different substrates.
Correlation between the optical and electrical parameters of ZnSe thin films
S. Venkatachalam,
Y. L. Jeyachandran,
V. SenthilKumar,
et al.
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ΩZinc Selenide (ZnSe) thin films are deposited onto the well cleaned glass substrates using vacuum evaporation method under a vacuum of 3 × 10-5Torr. Rutherford Backscattering Spectrometry (RBS) is employed to study the composition of the deposited film and the composition of the deposited film is found to be nearly stoichiometric. The deposited film is having cubic structure and is oriented along (111) direction. The particle size, strain and dislocation density are found to be 14.24 nm, 2.74 × 10-3lines/m2 and 4.9 × 10-3lines-2/m-4respectively. The optical band gap value is evaluated as 2.69 eV. The reflectance spectrum is obtained from the transmittance and absorbance spectra of the films. The refractive index value is calculated from the obtained reflectance spectra and is found to be in the range of 1.57 to 2.48. Drude’s theory of dielectric is used to calculate the values of carrier concentration, resistivity and mobility from the optical studies and the values are found to be 33.8 0× 1025m-3, 0.62 × 10-5Ωm and 33 × 10-3m-3respectively.
Fabrication of SiGe-on-insulator and applications for strained Si
Chenglu Lin,
Weili Liu,
Zhenghua An,
et al.
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SiGe-On-Insulator (SGOI) is an ideal substrate material for realizing strained-silicon structures that are very competing and popular in present silicon technology. In this paper, two methods are proposed to fabricate SGOI novel structure. One is modified Separation by Implantation of Oxygen (SIMOX) starting from pseuodomorphic SiGe thin film without graded SiGe buffer layer. Results show that two-step annealing can improve the cystallinity quality of SiGe and block the Ge diffusion in high temperature annealing. SGOI structure with good quality has been obtained through two-step annealing at 800°C+1350°C. The second method is proposed to achieve SGOI with high content of Ge. High quality strained relax SiGe is grown on a compliant silicon-on-insulator (SOI) substrate by UHCVD firstly. During high temperature oxidation, Ge atoms diffuse into the top Si layer of SOI. We successfully obtain SGOI with the Ge content of 38%, which is available for the growth of strained Si.
Investigation of laser-induced damage of dielectric optical coatings
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Investigation of laser-induced damage (LID) of dielectric optical coatings was reviewed in this paper. Several methods for evaluating characters of LID were developed, especially for the determinations of laser-induced damage threshold (LIDT) and the detections of absorption based on surface thermal lensing (STL) technology of optical coatings. Defect was deemed to be the initial source of several previous damage mechanisms, and was the main factor restricting the laser damage resistance of optical coatings. A pulsed laser induced damage model with a spherical absorptive inclusion was proposed in order to obtain the nature, size and distribution of defects. Attentions were paid to find out the origins of damage mechanism transformation from one laser mode to another. Moreover, interests were focused on distinct damage behaviors of ultraviolet (UV) lasers. Deposition temperature and annealing process in vacuum chamber had obvious influences on LIDT of the third harmonic Nd:YAG laser coatings. At the end of this paper, several effective methods for improving LIDT were put forward, such as cleaning substrate, improving deposition process, adding protective layers, optimizing coating stacks based on temperature field theory, as well as laser conditioning.
Vanadium oxide thin films prepared by RF magnetron sputtering method
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The vanadium oxide thin films were prepared by R.F. magnetron sputtering method under different deposition conditions. The microstructures of the samples have been investigated by XRD, XPS, and the Laser Scanning Confocal Microscope . By XRD and XPS, it was found that properly decreasing substrate temperature or increasing sputtering power, larger crystalline particle size and better crystalline orientation with V2O5 (001) after annealing can be gotten; Properly increasing substrate temperature or reducing sputtering power, the proportions of high valence vanadium oxides are increased. Based on our analyses, high-purity vanadium pentoxide films have been prepared by adjusting flux ratio of O2 and Ar, substrate temperature, and sputtering power.
The nanostructures and optical properties of ZnO films by RF magnetron sputtering
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ZnO nano films were deposited on SiO2/P-Si (100) by RF magnetron sputtering. The interrelationships among growth conditions, crystal structures, and optical properties of the ZnO films were discussed. The reflection spectra of the films reveal that the band-gap of the films is between 3.2-3.3eV. The photoluminescence spectra provide further evidence for the relation between the green emission of ZnO films and the oxygen vacancy or Zn interstitial related defects. The results also demonstrate that the UV emission of ZnO is dependent on the size of the nano-crystallites forming the films. By comparing with the photoluminescence spectra at low temperature, the possible mechanism for this dependent relation was discussed.
The study on the interface adhesion comparison of MgF2, Al2O3, SiO2, and Ag thin films
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Adhesion between the interface of pure silver thin film and three kinds of low refractive index coatings MgF2,Al2O3,SiO2 were compared in this article. The results indicated that the adhesion of Al2O3 and Ag was evidently superior to that of MgF2 and Ag ,and the adhesion of MgF2 and Ag was evidently superior to that of SiO2 and Ag. Reasons were analyzed accordingly. On the other hand, we compared the effect on the optical characteristic of Ag film when these three kinds of films were used as protective coatings and protective coatings. Considering the difference of the adhesion between Ag and MgF2,Al2O3,SiO2,suited uses are given for each other.
Study on the structure and ferroelectric properties of sol-gel-derived Pb(Mg1/3Nb2/3)O3-PbTiO3 thin films
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92%Pb(Mg1/3Nb2/3)O3-8%PbTiO3 (PMNT) thin films on Pt/TiO2/SiO2/Si substrates with and without a LaNiO3 (LNO) buffered layer have been prepared using a sol-gel method. Structures and electrical properties of these two films have been investigated and compared. Highly (111)-oriented PMNT thin films with some amounts of pyrochlore phase are obtained on bare Pt electrodes. On the contrary, (100)-oriented PMNT thin films with pure perovskite phase are formed on Pt electrodes with a LNO buffered layer. Electrical properties of the PMNT thin films are highly improved by using the buffered layer LNO. It is found that the remanent polarization (Pr) and the dielectric constant for the PMNT film with a LNO buffered layer are larger than that for the film without a LNO buffered layer.
Heat-treating effect on the properties of Pb1-xLax(Zr0.4Ti0.6)O3 ferroelectric thin film prepared by a modified sol-gel process
Fuwen Shi,
Genshui Wang,
Xiangjian Meng,
et al.
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2 mol% Lanthanum doped lead zirconate titanate Pb(Zr0.4Ti 0.6)O3 ferroelectric thin film were successfully deposited by a modified sol-gel method on(111) Pt/Ti/SiO2/Si(100) substrate, the effect of heat-treatment on the properties of microstructure and ferroelectric was investigated. It is shown that deposited on (111)Pt lead to (111) preferred orientation. The PLZT thin film annealing at 700°C show good ferroelctric properties with a large remnant polarization of 40μ C/cm2, a spontaneous polarization of 75.7μ C/cm2, and a coercive field of 112kV/cm under an electric field of 650kV/cm. The dielectric constant increased with annealing temperature.
Optical properties of BaTiO3 and Mn:BaTiO3 thin films deposited on fused quartz and silicon substrates using a sol-gel method
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The BaTiO3 and Mn:BaTiO3 thin films were fabricated on fused quartz and Si(111) substrates by a sol-gel method. The crystal structures of the samples were characterized by x-ray diffraction. It is shown that the samples are both polycrystalline thin films and possess cubic structure. The Mn-doping has no obvious effect on the crystal structure. The optical properties of the thin films were studied by transmitted spectrum technique or by spectroscopic ellipsometry depending on the substrate used. The transmitted spectrum shows that the absorption edge of the Mn-doping films has red shift compared with the undoping films. The energy gaps calculated from the transmitted spectrum are 3.68 and 3.39eV for undoping and Mn-doping samples, respectively. The results of spectroscopic ellipsometry shows that the refractive index of the Mn:BaTiO3 thin film is bigger than that of the BaTiO3 thin film. Which the change of energy gap and refractive index caused by Mn-doping can be explained by the Sellmeier Oscillator model.
Doped (AlxGa1-x)0.5In0.5P alloys grown by MOCVD
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Doped (AlxGa1-x)0.5In0.P alloys were grown by low-pressure metalorganic chemical vapor deposition (LP-MOCVD). It was demonstrated that the Zn-doped concentration in AlGaInP alloys was increased with the reducing of growth temperature and Al composition and the enhancing of dimethylzinc (DEZn) flow rate, also, the Si-doped concentration was reduced as the rising of growth temperature and silane (SiH4) flow rate.
Ion implantation into Si covered by HfO2 or SiO2 film
Hao Shi,
Min Yu,
Ru Huang,
et al.
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Ion implantations into HfO2 and SiO2 are simulated comparatively by using a molecular dynamics simulator LEACS. With precise physical models and high efficiency algorithms implemented in LEACS, the simulated results accurately agree with the SIMS data. Based on the verification of the LEACS simulator, Oxide Thickness Modulation Effect (OTME for short) has been quantitatively investigated by simulating implantations in HfO2/Si and SiO2/Si multiplayer structures, respectively. A much more drastic OTME for implantation in HfO2/Si is observed from simulation. It is found that if HfO2 replaces SiO2 as the gate dielectric, the shift of the range profiles in Si substrate is in the order of several 10%s of the total junction depth, which will have a significant impact on MOS device performance in IC process of next decade.
Influence of different bottom electrodes to microstructure and electrical properties of Pb(Zr0.52Ti0.48)O3 ferroelectric films
Jian-Kang Li,
Xi Yao,
Liangying Zhang
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LaNiO3 (LNO) thin films were successfully prepared on Si (100) and Pt/Ti/SiO2/Si substrates by metalorganic decomposition (MOD). The PZT thin films were spin-coated onto the LNO, LNO/Pt and Pt bottom electrodes by a modified sol-gel method. The crystallographic orientation and the microstructure of the resulting LNO films and PZT thin films on the different bottom electrodes were characterized by X-ray diffraction analysis. The dielectric, ferroelectric and leakage current properties of PZT films on the different bottom electrodes are discussed. The PZT films deposited on LNO/Pt/Ti/SiO2/Si and LNO/Si (100) substrates show strong (100) preferred orientation, while the films deposited on Pt/Ti/SiO2/Si substrates show (110) orientations. PZT films on LNO and LNO/Pt bottom electrodes have larger dielectric constant and remnant polarizations compared to those grown on the Pt electrode, but the leakage current of the films on Pt electrode are lower than that on LNO bottom electrode.
The preparation of the single-phase perovskite conductive LaNiO3 films on different substrates
Jian-Kang Li,
Xi Yao,
Liangying Zhang
Show abstract
LaNiO3 thin films were deposited on Si (100) and Pt(111)/Ti/SiO2/Si substrates by a modified metalorganic decomposition technique and rapid thermal annealing method. The structures of the films were characterized by x-ray diffraction (XRD). XRD analysis show that the LaNiO3 thin films on Si (100) and Pt(111)/Ti/SiO2/Si substrates possess single-phase perovskite-type structure and highly (100)-oriented. Scanning electron microscope (SEM) and atom force microscopy (AFM) image show the LaNiO3 films with uniform and crack-free surfaces. The resisitivity vs. temperature and thickness curves of the LaNiO3 films showed that the films possessed good metallic character.
Photoelectric properties of unsymmetrical metal-free phthalocyanine and C60 complex thin films
Zhigang Yang,
Yue Shen,
Jiancheng Zhang
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In this paper, novel one amino-group substituted unsymmetrical metal-free phthalocyanine (AUMPc) was synthesized, then the complex of AUMPc with C60 (The Complex) was obtained in the mixed solvents. Ultraviolet-visible (Uv-vis) spectrophotometer, fluorescence spectrophotometer and home-made photoconductivity meter were used to study the photoelectric properties of AUMPc and the complex. It was found that the absorbance of The Complex was larger than that of the total of AUMPc and C60 in the B belt (333nm), the absorbance of The Complex in the Q belt (693nm) where C60 had no absorbance was also increased. C60 took the role as annihilation in AUMPc, the photoconductivity of the Complex thin film was clearly increased when the film was exposed in the light.
Gallium phosphide protective infrared films on zinc sulphide deposited by RF-planar magnetron sputtering
Yangping Li,
Zhengtang Liu,
Hu Cui
Show abstract
GaP thin film has proved to be effectively protective coating for zinc sulphide long-wave infrared (8-11.5 μm) window or dome from sand abrasion and raindrop erosion. The GaP films are deposited on thermo-pressed 5-mm-thick planar ZnS substrates of 20 mm in diameter by RF-planar magnetron sputtering in high pure argon gas, with a single crystalline GaP disc of 50 mm in diameter as the target. Following parameters vary from experiment to experiment with others kept unchanged: input RF powers are increased from 30 W to 100 W as feeding gas flows and gas pressures in the vacuum chamber are decreased simultaneously, with the intensity of the 750-nm-wavelength ray of argon's OES observed through a CCD multichannel spectrometer in glow discharges remaining almost the same. Thus different sets of deposition parameters are gained. Within these sets of parameters, the deposition rates and the degree of crystallization of the films increase with the input RF power increasing, as the IR transmission performances are as good, and thus thick GaP films with little absorption are achieved. SEM analyses show that the GaP films are compact and glazed.
The phase transformation and mechanical behavior of NiTi thin films
Show abstract
The phase transformation and superelastic properties of NiTi thin films prepared by sputtering were studied. Thin films’ phase transformation process was analyzed with resistance temperature curves and X-ray diffraction spectroscopy. Meanwhile, the structure and transformation temperature were gained. In order to characterize their superelasticity, tensile and bulging and indentation test were performed.
Microstructure and properties of sol-gel-derived (La,Sr)CoO3 thin film with compositional fluctuation La/Sr ratio
Wei Lu,
Ping Zheng,
Zhongyan Meng,
et al.
Show abstract
Thin films of Lanthanum strontium cobalite [(La1-xSrx)CoO3, LSCO] were directly spin-coated onto SiO2/Si (1 0 0) substrates with compositional fluctuation La/Sr ratio, followed by rapid thermal annealing (RTA). The effects of different La/Sr ratios on the microstructure, surface morphology and electrical properties of the films were examined by X-ray diffraction (XRD), scanning electrical microscopy (SEM) and four probe measurements, respectively. The results indicate that the thin film displays a structure transform from rhombohedral phase to cubic phase around x=0.5, and that the resistivity of the thin film decreases with the increase of La/Sr ratio at the first, then increase slightly. A minimum value of resistivity of LSCO appears at x=0.5. In addition, the effect of the annealing temperature on the electrical properties of La0.5Sr0.5CoO3 films is discussed.
Thickness-dependent electrical properties of lead zirconate titanate thin films on titanium substrates
Ping Zheng,
Jinrong Cheng,
Wei Lu,
et al.
Show abstract
Ferroelectric lead zirconate titanate Pb(Zr0.53Ti0.47)O3(PZT) thin films with various thicknesses have been fabricated on Ti substrates by using the sol-gel method with a rapid thermal annealing process (RTA). A thin layer of LaNiO3 (LNO) thin film was introduced between PZT and Ti substrate. Results indicated that PZT thin films on Ti maintained strong dielectric and ferroelectric properties. With increasing the film thickness, the dielectric constant K of PZT thin films increases, so does the leakage current density. The value of K is of 1050 and 1500 for 0.7 and 2.1 μm thick PZT thin films respectively. The remnant polarization Pr of PZT thin films achieved around 55 μC/cm2, and the coercive field Ec decreased with increasing the film thickness.
Influence of buffer layer on dielectric properties of (Ba1-xSrx)TiO3 thin films
Dongwen Peng,
Zhongyan Meng,
Wenbiao Wu
Show abstract
Ba0.6Sr0.4TiO3 thin films with Ba1-xSrxTiO3 (1-x = 0, 0.4 0.5, 0.6, 0.7) buffer layers were deposited on LaAlO3 (LAO) substrates by sol-gel techniques, respectively. The effects of compositions and thickness of buffer layers on the dielectric properties of BST films were discussed. Films were characterized by X-ray diffraction technique (XRD), field emission scanning electron microscope (FE-SEM) and dielectric measurements. It was found that the structure and properties of films varied with different compositions of buffer layer. The Film Ba0.5Sr0.5TiO3 buffer layer of 20 nm in thickness has higher tunability (31.2 %), lower dielectric loss (0.006), and larger FOM of 52 at 1MHz by applied DC bias electric field of 60 KV/cm. As the thickness of the buffer layer increased to 60 nm, the phase structure of buffer layer materials would influence the dielectric properties of the main films.
Study on the stress of silicon nitride thin films prepared by PECVD
Ying Yu,
Zongzi Luo,
Xinqiao Weng
Show abstract
The residual stresses on silicon nitride thin films that were fabricated by PECVD were studied in this paper. A wafer-curvature measurement method was used to determine the stresses of silicon nitride films. The structure of fixed-fixed beam was also developed to compare with the stress measurement. The contributions of processing parameters on the stress of silicon nitride films were analyzed.
Photoconductivity of azo-polymer-copper-phthalocyanine-diamond-like carbon films
Yue Shen,
Jiancheng Zhang,
Yiben Xia,
et al.
Show abstract
The influence of the azo-polymer on photoconductivity of the copper phthalocyanine (CuPc) film is studied. The result show that the photoconductivity of the film added with azo-polymer layer has increased by one order of magnitude in several seconds. The diamond - like (DL) carbon flim was used as a passivation film.
The preparation of diamond films on new composite ceramic substrates of diamond and alumina
Yue Shen,
Yiben Xia,
Feng Gu,
et al.
Show abstract
This paper reports the preparation and properties of diamond films deposited on new composite ceramic substrates of diamond and alumina. The influences of the substrates to the properties of diamond films were discussed. The Raman spectra and SEM show that the substrates which prepared by hot pressing sintering were more suitable to deposit high quality diamond films. The main reason why diamond films deposited on composite ceramic substrates without any pre-treatment have good qualities and why the composite ceramic substrate is appropriated to deposit large area diamond films are studied.
Ferroelectricity of BiFeO3 prepared by the chemical solution deposition method
Caixia Yang,
Yinyin Lin,
Ting-ao Tang
Show abstract
Bismuth ferric thin films were fabricated on Pt/Ti/SiO2/Si substrates by the chemical solution deposition Technique. The films were annealed at different temperature using a rapid thermal processor. DTA-TG and DSC-TG were used to study the reaction and crystallization during the process. The influence of the preheated process and annealing temperature on the structure and the morphology of the film were discussed. XRD and SEM were employed to investigate the crystal structure and the phase of the films annealed at different temperatures. The pure phase BiFeO3 thin films were obtained when the film was annealed under the temperature of 800°C. Saturated ferroelectric hysterersis loops are observed. The spontaneous polarization and remnant polarization are 6.9μC/cm2 and 2.8μC/cm2 respectively.
The studies of RT electrical resistivities of LaNiO3-δ thin films by RF magnetron sputtering with different percentage of oxygen partial pressure at various substrate temperatures
Show abstract
Electrically conductive LaNiO3-δthin film with perovskite-type structure were deposited on Si(100)/n substrates by rf magnetron sputtering at substrate temperature 200°C , 300°C, 450°C, 600°C with a series of 0%, 20%, 40%, 60% oxygen partial pressure respectively. The La2NiO4 and NiO peak of XRD are not observed. The RT resistivity of LNO films decreases with the decreasing substrate temperature at a fixed oxygen partial pressure and with increasing oxygen partial pressure at a fixed substrate temperature.
Formation mechanism of the VO2 polycrystalline film prepared by modified-ion-beam enhanced deposition
Show abstract
A new method of modified Ion Beam Enhanced Deposition (IBED) was designed to form VO2 polycrystalline film with good properties. While argon ion beam sputtered V2O5 powder target to deposit vanadium oxide film, a high current Ar+/H+ mixing beam with a high dose was implanted into the deposited film. The VO2 film with the Temperature Coefficient of Resistance (TCR) as high as 4%/K was obtained after subsequent appropriate annealing at the temperature above 500°C. The formation mechanism of the IBED VO2 film was discussed as following: the damage effect of the argon ion beam implantation broken some of V-O bands; The deoxidization effect of implanted hydrogen reduced V2O5 to VO2. The mixing effect could make IBED film adhere to the substrate firmly. The doping effect of the implanted argon introduced stress in the film to decrease the phase transition temperature. The bombardment effect made the film more compact, decreased oxygen vacancy density, reduced the grain boundary width, and increased the TCR of the IBED VO2 polycrystalline films.
The transmission of organic group in solid electrolyte film
Shuo Shi,
Guo-Sheng Zhang,
Jia-Lin Sun,
et al.
Show abstract
We found a new solid electrolyte K-Cu-I thin film which can transmit the organic group (OG). The film was prepared by depositing a mixture of KI and CuI powders on heated glass substrate in vacuum. Under direct current (DC) electric field, the OGs can migrate toward cathode through the K-Cu-I film and congregated at the edge of the cathode. At room temperature, the film had an OG conductivity that can reach up to 0.15Ω-1cm-1 when the electron conductivity was ignorable (σ≤10-4Ω-1cm-1).
Thickness effect of LaNiO3 buffer layer on microstructure and electrical properties of PZT thin films
Wenjuan Du,
Wei Lu,
Jinrong Cheng,
et al.
Show abstract
The thickness effects of (LaNiO3) LNO buffer layer on microstructure and electrical properties of PZT thin films were investigated. XRD patterns show that the orientation of PZT films directly prepared on the random-oriented Pt coated substrates exhibits random orientation, and that the PZT films with buffer layer reveal (100) preferred orientation to match with the (100)-oriented LNO buffer layer. Moreover, (100) orientability arises higher and the grain size becomes smaller with increasing thickness of LNO layer. As a result, the higher dielectric constant is obtained. The improvement of fatigue behaviors is due to that LNO thin films can alleviate the oxygen vacancy accumulation at the ferroelectric-electrode interface.
Structural and electrical properties of Pb(Zr,Ti)O3 thin films on NiCr substrate modified by LaNiO3 and PbTiO3 buffer layers
Liang He,
Jinrong Cheng,
Zhongyan Meng
Show abstract
Ferroelectric Pb(Zr,Ti)O3 (PZT) thin films were deposited onto the NiCr (NC) substrate by using sol-gel techniques. LaNiO3 (LNO) and PbTiO3 (PT) buffer layers have been introduced to grow single-phase perovskite PZT thin films at the lower temperature of 550°C. The (110) preferred orientation of PZT thin films was favored using LNO and PT buffer layers. Dielectric constant and remnant polarization of PZT thin films on NC with a LNO buffer layer achieved ~ 430 and 13 μC/cm2 respectively. The ferroelectric P-E loops of PZT thin films were shifted towards the positive field by introducing LNO buffer layers. In addition, the coercive field and internal bias field increased with increasing the thickness of LNO layer.
Tunable properties of PbxSr1-xTiO3 thin films
Boyu Ni,
Dongwen Peng,
Wenbiao Wu,
et al.
Show abstract
Lead strontium titanate (PbxSr1-xTiO3) thin films with Pb/Sr ration of 10/90, 20/80, 30/70 and 40/60 were deposited on Pt/Ti/SiO2/Si substrates by sol-gel techniques. Both structural and dielectric properties of PST films as a function of Pb/Sr ratios were investigated. PST thin films showed typical polycrystalline structure without preferential orientation. The measured capacitance and tunability systematically increased with the increase in Pb content. Among all the PST thin films, PST (30/70) thin film has the best crystallization and dielectric properties. The dielectric constant, dielectric loss tenability and FOM of the PST (30/&70) film are 376,0.022, 61.0% and 28, respectively.
Preparation and characterization of chemically deposited SnS thin films
Jing Xu,
Guangpu Wei,
Weiming Shi,
et al.
Show abstract
Tin Sulphide is a promising material for use in solar cell with its suitable band gap energy and high absorption coefficient. In this paper, we prepared thin films of SnS by chemical bath deposition and annealed them at 300°C in N2 atmosphere. The SnS thin films were characterized structurally, optically and electrically. XRD shows the as-prepared film had orthorhombic crystal structure, exhibited Sn-rich composition and partially transformed to SnO2-xby thermal treatment. The absorption was found to be as high as 105cm-1for the photon energy above 1.55eV and the optical band gap was estimated to be 1.45eV from the transmittance spectra. The dark-and photo-conductivity were also calculated from the I-V curves of the as-prepared and thermal-treated films.
Preparation and characterization of Nd-doped Bi4Ti3O12 thin films by pulsed laser deposition method
Wen Biao Wu,
Zhong Yan Meng,
A. Shibuya,
et al.
Show abstract
Perovskite Neodymium-modified Bi4Ti3O12 (BNdT) thin films were prepared on Pt/TiO2/SiO2/Si substrates by the pulsed laser deposition (PLD) technique, and their structures and ferroelectric properties were investigated. The remnant polarization was increased with Nd-modification. The remanent polarization (2Pr) and coercive field (2Ec) of BNdT thin films are 78 μC/cm2 and 619 kV/cm, respectively. The good fatigue behavior of BNdT films has been obtained. The reduction of remanent polarization of +Pr and -Pr is smaller than 25 % after 1010 switching cycles. The effect of substrate temperature and laser repetition frequency on the structure and ferroelectric properties is remarkable.
Synthesis and applications of ordered mesoporous tin dioxide thin films
Xiao'an Zhou,
Jiancheng Zhang,
Yue Shen
Show abstract
Tin alkoxides are precursors used as preparing thin films by the sol gel method. In this paper, the author has prepared tin alkoxides by the reaction involving alcoholic solutions of tin chloride with ammonia gas. The ordered mesoporous tin dioxides also have been synthesized by the alcoholic sol-gel method from the precursors. Using the dip coating method, thin films have been uniformly deposited on some substrates, such as glass, silica and so on. X-ray diffraction (XRD), differential thermal analysis (DTA) and infrared spectroscopy (IR) microscopy have been used to characterizing the mesostructures and morphology formed under the room temperature as well as calcinations at different temperature. The surface areas of material, evaluated from Brunauer Emmett Teller (BET) formula .indicated the surface areas about 296m2/g and 176m2/g for calcinations at 350°C and 400°C respectively. In addition, the gas-sensing properties of thin film sensor of the mesoporous SnO2 have been investigated. The results indicated the sensitivity of mesoporous SnO2 sensor was superior to that of a conventional non-porous SnO2.
Preparation and properties of hydrophobic organic-inorganic silica hybrid films
Lanfang Yao,
Guangming Wu,
Zhaofeng Wu,
et al.
Show abstract
Hydrophobic organic-inorganic silica hybrid films were prepared by means of a two-step acid-catalyzed method and sol-gel process using surfactant as template. Methyltriethoxysilane(MTES) and tetraethoxysilane(TEOS) were co-hydrolyzed in different molar ration and were used as precursors. Addition MTES in TEOS precursors produces a decrease of Si-OH and Si-O- surface content. The infrared spectra of the films thus obtained indicated that they become hydrophobic with the introduction of the methyl groups. Contact angle instrument was also used to supplement the result. Contact angle values for hydrophobic hybrid films are greater than 120° . The refractive indices and thickness of hydrophobic hybrid films are about 1.22-1.24 and about 270-300nm The Optical transmittance spectra and mechanical intensity measurement results showed that the films have good optical and mechanical properties.
Preparation of low-density porous silica thin films by ambient pressure drying
Show abstract
Low-density silica thin films having densities ρ of 0.574-0.957(g/cm3 )and refractive indices n of 1.12-1.20 and porosities ∏ of 61%-77% as well as dielectric constants k of 1.92-2.54 were prepared by a two-step sol-gel process at ambient pressure, with a simple dip-coating procedure, which take the wet gel through solvent exchange and reaction with trimethylchlorosilane(TMCS) without any supercritical drying. The process was optimized by varying the dilution, aging, organic substitution, organic modification, heat treatment and dip-coating conditions. Ellipsometer was used to determine refractive index and thickness of films. Atomic force microscopy (AFM) used to observe the microstructure and surface of thin films. Infrared spectroscopy and anti-reflectance measurement was carried out too. Abrasion-resistant properties were tested by the methods suggested by Floch et.al .
MgB2 thick film grown on stainless steel substrate with ductility
Qing-rong Feng,
Chinping Chen,
Ying Lu,
et al.
Show abstract
MgB2 thick film was synthesized on the stainless steel substrate by the technique of hybrid physical-chemical vapor deposition (HPCVD), using Mg ingot and B2H6 as the raw materials. The film thickness is about 10 μm. The scanning electron microscope (SEM) images reveal that it is consisting of highly dense MgB2 crystals with the size ranging from 0.2 to 3 μm. The superconducting transition occurs at 38 K (Tc, onset) and ends at 27 K (Tc, zero), giving the transition width of 11 K. The fabricated film exhibits high ductility and remains attached to the substrate after it was bent to a curvature of about 200 μm.
Structural ordering in amorphous silicon thin film due to post hydrogen plasma annealing
Yunjun Rui,
Jiaxin Mei,
Jun Xu,
et al.
Show abstract
The effect of hydrogen plasma annealing on the microstructural transition from disorder to order in amorphous silicon film is studied in this paper. Combined with the Fourier Transmit Infrared spectroscopy, Raman scattering and absorption spectra, it is found that there exists two steps for the reaction between atomic hydrogen and Si network. It is shown that the hydrogen plasma treatment conditions strongly influence the microstructures of the amorphous Si films.
Characterization of vacuum-evaporated In70Se30 thin films
C. Viswanathan,
S. Gopal,
B. Karunagaran,
et al.
Show abstract
This paper discusses the properties of thermally evaporated polycrystalline In70Se30 thin films (Tsb=303-473K). Structural and surface morphology of the film were identified by X-ray diffractogram and Scanning Electron Microscopy. The composition was verified by EDAX and XPS spectrum. The results of conductivity measurements (Tsb =303K) have
revealed that thermionic emission and variable range hopping (VRH) are the two dominant conduction mechanisms in the
temperature ranges of (230-280 K) and (170-220 K) respectively.
Effect of oxygen implantation on the characteristic of Ge2Sb2Te5 phase change film
Bo Liu,
Zhitang Song,
Ting Zhang,
et al.
Show abstract
Ge2Sb2Te5 films were deposited by RF magnetron sputtering on Si (100)/SiO2 substrates. O+ ion was implanted into Ge2Sb2Te5 films. It is indicated that the structure of crystalline Ge2Sb2Te5-O annealed at 250°C is still identified as a FCC structure and the lattice parameter increases with the increasing oxygen implant dose. However, phase separation takes place when annealing temperature is 450°C. Oxygen implantation has great effect on the resistance of Ge2Sb2Te5 film. Due to oxygen doping, the resistance of Ge2Sb2Te5 film decreases when annealing temperature is lower than 300°C because the FCC unit cell was distorted by oxygen atom occupying the tetrahedral interstitial site and the defects were increased, which results in larger number of current carrier. However, resistance of Ge2Sb2Te5 film increases when annealing temperature is higher than 340°C, which may be caused by phase separation and current carrier being scattered by crystallite boundary.
Mesoporous silica thin films prepared by argon plasma treatment of sol-gel-derived precursor
Jian Zhang,
Al Palaniappan,
Xiaodi Su,
et al.
Show abstract
Argon plasma is used to generate the mesoporous silica thin films from sol-gel-derived precursor. Poly(ethylene glycol)(PEG, MW=400) is employed as the template, i.e., the pore directing-agent as well as the binder. The influence of the plasma parameters on the mesoscopic properties of silica films are investigated by scanning electron microscopy (SEM), FTIR, low-angle X-ray scattering (SAXS), and nitrogen isotherm adsorption.
The influence of rapid recurrent thermal annealing on magnetic properties of CoFe-O thin film
Yu Shi,
Huaiwu Zhang,
Yulan Jing,
et al.
Show abstract
The variation of magnetic properties with a new rapid recurrent thermal annealing (RRTA) were studied in high moment thin film (Co 0.35Fe0.65)99O1. After the rapid recurrent thermal annealing at 450°C for several periods of times, the coercivity as-deposited this thin film decreased from 105 to 3 Oe, and their resistivity was decreased to 70 percent. It is found that the method is more effective than other methods to improve the magnetic and electrical properties of (Co0.35Fe0.65)99O1 thin films.
Structure and ferroelectric properties of Bi3.25La0.75Ti3O12 and Bi3.25Nd0.75Ti3O12 thin films prepared by an MOD method
Show abstract
The structure and ferroelectric properties of Bi3.25 La 0.75Ti3O12 (BLT) and Bi3.25 Nd0.75Ti3O12 (BNT) thin films deposited on (111)Pt/Ti/SiO2/Si substrates using a metalorganic decomposition (MOD) method were investigated. Both the films were polycrystalline structure with the single bismuth-layered phase. The BNT film showed the (117) random orientation, while the BLT film displayed (00l)-preferential orientation. The BNT film showed a larger remnant polarization (~13.8μC/cm2) than the BLT film (~3.5μC/cm2), while both films displayed almost the same value of coercive field. The BNT film had the larger dielectric constant and a litter larger dissipation factor than the BLT film. The superior ferroelectricity of the BNT film was mainly attributed to its (117) random orientation. Furthermore, the BNT film displayed good fatigue endurance up to 109 switching cycles, indicating it was a useful candidate for integrated device applications.
Nodule growth in zirconium films prepared by ion beam sputtering
Show abstract
Zirconium films were deposited by ion beam sputtering method. A novel substrate holder was designed to realize the approximately in-situ observation the process of the nodule growth. The method of pre-setting particle seeds on the substrates was used in the film deposition. Optical microscope and SEM were presented in observation the specimen before and after annealing. An interesting growth mode of nodules which different from the reported in science literature was found in our experiment. The molecule dynamics theory and diffusion limited aggregation (DLA) model was presented to analysis this phenomenon.
Influences of post-deposition annealing on the properties of the ZrO2 thin films prepared by electron beam evaporation
Show abstract
The ZrO2 thin films were deposited on BK7 glass substrates by electron beam evaporation method at room temperature. The influences of post-deposition annealing between 200°C and 400°C on the structural and mechanical properties of the films have been investigated by X-ray diffraction and atomic force microscopy. It was found that a monoclinic phase formed at lower temperature of 200°C. With the increase of the annealing temperature, the tetragonal phase appeared. The stress in ZrO2 films showed a transition from tensile to compressive which could be explained as the evolution of the microstructure as function of annealing temperatures. At the same time, the refractive index of the ZrO2 films increased with the increasing of annealing temperatures, which may be ascribed to the microstructure densification of the ZrO2 films.
Fabrication and characteristics of PLZT thin films derived from MOD process
Show abstract
Crack free PLZT (9/65/35) thin films were prepared by a metallic organic decomposition (MOD) process on Pt(111)/Ti/SiO2/Si(100) and sapphire(001) substrates respectively. The films on Pt/Ti/SiO2/Si substrates present highly (111)-preferred orientation while they display highly (110)-preferred orientation on sapphire substrates. The microstructure of the films were investigated and discussed. Ferroelectric properties of PLZT thin films on Pt/Ti/SiO2/Si(100) substrates have been studied. Typical slim polarization-electric field hysteresis loops were observed. As the film thickness increasing, the remanent polarization Pr increases and the coercive electric field Ec drops. The influence of film thickness on optical transmittance and refractive index nr were examined by the films deposited on sapphire substrates. The nr at 510nm wavelength shows an increasing tendency with film thickness increasing. Great stress aggregated during the film processing is thought to be an important reason which results in the variations of optical properties dependent on the film thickness.
Influence of process parameters on fabrication of PZT(53/47) thick films by a dip-coating process
Show abstract
Crack-free polycrystalline PbZr0.53Ti0.47O3 (PZT(53/47) thick films (1~30μm) with peroviskite structure have been prepared from a dip-coating process. The influence of withdrawal speed and precursor solution concentration on the morphology of the films was examined. The effects of the substrate characteristics on the film phase structure and microstructure were investigated and evaluated. The ferroelectric and dielectric properties have been examined and discussed. PZT (53/47) thick films on Pt/Ti/SiO2 wafer and Pt/Ti foil substrates all exhibit excellent electric properties, Pr: 32~34 μmC/cm2; Ec: 32~35kV/cm, εr 900~940; tanδ: 0.02~0.04. These materials promise a good application in micro-devices including micro-pump, micro-actuator, etc.
Anisotropic optical properties of ZrO2 films by oblique deposition
Show abstract
The ZrO2 thin films are prepared by oblique deposition. Spectrophotometry yields an obvious anisotropic p-polarized transmittance. On the computation of refractive indices of different incidence angles and polarization states, the anisotropic optical properties are obtained. The refractive indices derived from s-polarized light are around 1.725, but the ones for p-polarized light are from 1.82 to 1.94. The distribution of refractive indices is consistent with the transmittance of s- and p-polarized light. The transmittance of ZrO2 thin films by oblique and normal deposition are compared each other. The results could be qualitative understood from the presence of an inclined column with shape birefringence.
Thin Film Technology
Plasma-implantation-based surface modification of metals with single-implantation mode
X. B. Tian,
J. T. Cui,
S. Q. Yang,
et al.
Show abstract
Plasma ion implantation has proven to be an effective surface modification technique. Its biggest advantage is the capability to treat the objects with irregular shapes without complex manipulation of target holder. Many metal materials such as aluminum, stainless steel, tool steel, titanium, magnesium etc, has been treated using this technique to improve their wear-resistance, corrosion-resistance, fatigue-resistance, oxidation-resistance, bio-compatiblity etc. However in order to achieve thicker modified layers, hybrid processes combining plasma ion implantation with other techniques have been frequently employed. In this paper plasma implantation based surface modification of metals using single-implantation mode is reviewed.
Thermal stability of metal containing diamond-like carbon thin film fabricated by dual plasma deposition
Ricky K. Y. Fu,
Y. F. Mei,
M. Y. Fu,
et al.
Show abstract
Diamond-like-carbon (DLC) films have an amorphous structure comprising a sophistical carbon matrix and have attracted a great deal of scientific interest. Metal-doped DLC (Me-DLC) can possess superior properties as metal nanoclusters or nanocrystalline metallic carbides can be embedded in the carbon network. Therefore, Me-DLC exhibits good adhesion to the substrate, high hardness, low friction coefficient and high magnitude of conductivity. In this work, a metal cathodic vacuum arc and acetylene dual plasma are synchronized to produce Me-DLC. We systematically fabricate the Me-DLC films by varying the acetylene flow rate and substrate bias voltage. Our results acquired by Rutherford backscattering spectrometry (RBS) show that the film thickness and metal content can be controlled by the process windows. Four point probe measurements illustrate a decrease in the resistivity with increasing metal content whereas x-ray photoelectron spectroscopy (XPS) and x-ray diffraction (XRD) results show the formation of carbide phases in the carbon matrix. To evaluate the thermal stability of the thin film, both undoped DLC and Me-DLC films are annealed at a series of temperature in argon ambient. Raman scattering results reveal that the Me-DLC films can tolerate a high annealing temperature without serious graphitization. It is believed that metals incorporation retards the restructuring of the carbon matrix during the annealing processes.
Development and applications of solar cell in China
Guangpu Wei,
Deng-Ren Jin
Show abstract
In China, the Research and Development (R&D) of solar cell and photovoltaic (PV) system were started in 1958. At the beginning of 1970’s, c-Si (crystal silicon) solar cells with efficiency about 13%(AM0) had been made out and then successfully used in the Chinese satellite launched in 1971. After more than 40 years’ effort, now about 40 institutes, universities and companies are engaging in the PV works. Until the end of 2003, about 12 solar cell plants with certain scale had been established. The annual production capacity of solar cells/modules was about 12 MW and the total installed capacity of PV system was about 50MW. The highest efficiency of 20.4% for c-Si solar cell ever reported.
Organic light-emitting devices using phosphorescent dopants
Takao Nagatomo,
Susumu Nagashima,
Ryosuke Sugawara
Show abstract
The EL properties of organic light-emitting devices using phosphorescent dyes as a guest material are described. Poly(9-vinylcarbazole) (PVCz) in the polymer system and 4,4’-N,N’-dicarbazolbiphenyl (CBP) in the low molecular system are used as a matrix. Perylene, 4-dicyano-methylene-2-methyl-6-4-dimethylami-nostyryl-4H-piran (DCM1), bis (4-phenylimidazopyridine)beryllium (Be(PIP)2) and etc. are used as a fluorescent dopant and/or iridium-complexes: (tris-(2-phenyl-pyridine)iridium) (Ir(ppy)3), iridium(III)bis[(4,6-di-fluorophenyl) pyridinato-N,C2’] picolinate (FIrpic) and bis(2-(2’-benzo[4,5-a]thienyl)pyridinato-N,C3’)iridium(acetylacetonate) (btp2Ir(acac)) are used as a phosphorescent dopant. In the ITO/PVCz:DCM1, Be(PIP)2/Alq3/Al devices with DCM1(0.5mol%constant) and Be(PIP)2(variable), the peak wavelength does not change by the doping of Be(PIP)2 and the EL intensity becomes maximum at 0.5mol% doping and increases in comparison with the case with non-doped at 2 digits. These results indicate that Be (PIP)2 does not emit itself and roles to transfer the excited energy to the emitting centers (emitting assist). The EL properties of organic light-emitting diodes (OLEDs) using PVK as a matrix (host) and phosphorescent materials (btp2Ir(acac) and Ir(ppy)3) as a guest material are remarkably improved in comparison with OLEDs doped btp2Ir(acac) (guest) into PVK (host).
The effects of ion cleaning on the roughness of substrates and laser induced damage thresholds of films
Show abstract
The ion cleaning effect on the roughness of substrates and laser induced damage thresholds (LIDT) of films were investigated. It is found that ion cleaning has different effects on the roughness of substrates with the different ion cleaning time, and it improves the LIDT of single layer films greatly.
Selective formation of porous silicon array using highly resistive silicon layer as masking materials
Xiaohua Wang,
Shaoqiang Chen,
Jian Zhang,
et al.
Show abstract
A new technology using ion implantation technique to create the selectively patterned porous silicon structures is presented in this paper. Hydrogen ions were first selectively implanted into silicon substrates and resulted in a highly resistive silicon layer. This layer can be used as a mask to selectively etch the un-implanted areas by electrochemical etching of crystalline silicon in HF-based solutions and lead to the formation of PS arrays. The quality of resulted PS were characterized by the analysis tools like SEM, AFM, etc. It is concluded that the ion implanted silicon can be used as the mask material for the selectively formation of PS patterns. The masking capability of the implanted Si layer is dependent upon the implantation conditions. The relationship between the masking capability of highly resistive silicon layer and the implantation condition (parameters like dose, time) were discussed. The developed technique is quite simple and can be used to form the fine PS patterns.
Field emission behavior of GaN nanoparticles and nanobelts
Ke Yu,
Yongsheng Zhang,
Laiqiang Luo,
et al.
Show abstract
Gallium nitride (GaN) nanoparticles and nanobelts films are successfully synthesized on Si (111) substrates through ammoniating Ga2O3 thin films deposited by radio frequency magnetron sputtering. X-ray diffraction (XRD), scanning electronic microscope (SEM), transmission electronic microscope (TEM) are carried out to analyze as-synthesized GaN products. The field emission measurements show that the as-synthesized GaN nanoparticles and nanobelts have lower turn-on field of 5.8 and 6.1V/μm at the current density of 0.1μA/cm2, respectively. It is found that the Fowler-Nordheim (FN) plot of nanobelts exhibits nonlinearity. The experimental results demonstrated that there were great potential applications of the GaN nanoparticles and nanobelts for flat panel displays.
Preparation and performance of phase retarder at the wavelength of 1315-nm
Show abstract
The periodic dielectric phase retarders that produce a ±90° phase shift between the p- and s- polarization components at the incident angle of 54° and the wavelength of 1315nm while maintaining high reflectivity for both components are designed. An optimization technique has been used to determine the layer thickness for a coating design that produce a 270±1° phase shift between the p- and s- polarization components over 1285-1345nm while the average reflectivity is over 99.5%. Then the designed retarders were prepared by ion beam sputtering (IBS), and the phase shift was 262.4±1.8° and the reflectivity was over 99.6% at the design waveband.
Epitaxial growth of atomically smooth (111)-oriented MgO films on Si (111) substrate by pulsed laser deposition
Tong Lai Chen,
Xiao Min Li,
Xia Zhang,
et al.
Show abstract
(111)-oriented MgO thin films have been deposited on Si (111) substratres by pulsed laser deposition (PLD). The whole growth process of the films was in-situ monitored by using reflection high energy electron diffraction (RHEED) apparatus. The films were characterized by X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). Furthermore, the leakage current measurement of MgO films was also performed. Completely (111)-oriented MgO films with atomically smooth surfaces were obtained. The HREED observations show that the growth mode of the MgO films is 2D layer-by-layer growth. And the I-V characteristics evidenced the excellent crystallinity of the MgO films.
Temperature dependence of laser-induced damage threshold of 355-nm Al2O3/MgF2 HR coatings
Show abstract
Laser-induced damage threshold (LIDT) of 355nm was a more severe problem than that of 1064nm. This work had been carried out to obtain high LIDT and high reflectance for Al2O3/MgF2 quarter wave multilayer stacks (35 layers). All the samples were deposited by electron beam evaporation using the same deposition process at different deposition temperatures. LIDT was measured by using a 355 nm Nd:YAG pulsed laser with a pulse width of 8 ns. It was found that deposition temperature had a fundamental effect on the thresholds of HR coatings. LIDT up to 18.5J/cm2 was achieved when the deposition temperature was 280°C. Transmittance and high reflectance of the samples were measured by Lambda 900 Spectrophotometer and the high reflectance of 98.7% was achieved. An absorption dominated model was proposed which met the results of damage thresholds.
Characterization of ZnO films grown on different substrates by L-MBE method
Show abstract
ZnO films were fabricated using Laser molecular beam epitaxy method on different substrates including Si(001), C-plane and R-plane Al2O3. The crystallinity and orientation of the films, as well as the epitaxial relationship between ZnO films and the substrate were studied using X-ray diffraction (XRD) technique. For the films grown on C-plane Al2O3 and Si(001) substrates, Highly c-axis oriented ZnO films were obtained. The surface morphology and roughness of ZnO films were determined by atomic force microscopy (AFM) and Reflection High Energy Electron diffraction (RHEED).
Influence of inhomogeneities on the spectral characteristics of anti-reflection coatings
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The influence of inhomogeneous transitional layers on the spectral characteristics of AR coatings is discussed in this paper, and some results have been got: Inhomogeneous layers between substrate and coatings results in decreasing of the anti-reflection performance along with extremum shift to short wavelength; and among several kinds of inhomogeneous layers between two coatings, sine transition increases the anti-reflection performance, linearity, hyperbolae and exponent decrease the anti-reflection performance. Then a good fitting was given to the experiment of AR coatings and it was discovered that the sine transition between substrate and coatings is similar to experiment very well.
Elimination of the half-wave hole for short-wave pass filter
Show abstract
A few reasons to cause the half-wave hole for the short-wave pass filter had been analyzed. According to these reasons, the application of a new admittance-matching method and a photoelectric maximum control with half-wavelength effectively eliminated the half-wave hole. The matching stack consisted of a symmetrically periodic structure and provided a complete matching at the desired wavelength; i.e., both conditions for the equivalent admittance and phase thickness were fulfilled. Furthermore, both the theoretical and the tested curves had been given, and a good agreement between them was obtained.
Properties of InGaN violet-LED structure
Show abstract
The violet-LEDs structure with InGaN/GaN multi-quantumn-wells (MQW) was grown by low-pressure metalorganic chemical vapor deposition (LP-MOCVD). The x-ray diffraction (XRD) revealed distinct second order satellite peak. The photoluminescence (PL) wavelength was about 399.5nm with FWHM of about 15.5nm. InGaN/GaN MQW violet-LEDs have been successfully fabricated with EL wavelength of 402nm and forward voltage about 3.6V under 20 mA injection current.
Optical properties of Al2O3 and MgF2 coatings deposited by electron-beam evaporation in the DUV/VUV spectral range
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Single layers of Al2O3 and MgF2 were deposited upon super polished fused-silica by electron-beam evaporation and were characterized. The subsequent optical constants n and k were reported for the spectral range of 180nm-230nm. And HR coatings for 193nm were designed on the basis of the evaluated optical constants and produced. Transmittance and reflectance of HR coatings were compared to the theoretical calculations on the basis of the evaluated optical constants of the single layers.
Preparation and characterization of [100]-oriented diamond films by HFCVD
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In this paper we report high quality [100]-oriented diamond films prepared by HFCVD using hydrogen as carrier gas and C2H5OH as carbon source for the first time. The surface morphology observed by SEM showed polycrystalline diamond films with [100] faced structure with an average grain size of ~20 μm. The Raman spectrum indicated sp3 bonding with a sharp peak at 1333 cm-1. The I-V characteristics obtained via Au contact were determined by semiconductor characterization system. The electrical resistivity of HFCVD [100]-oriented diamond film was ~3.0x1010Ω cm. The capacitance and dielectric loss of films were very small with the value of 2.0pF and 0.02, respectively, and almost had no dependence with the change of frequency in high frequencies.
Generation of 32-fs pulse by use of optimized Gires-Tournois interferometer negative-dispersion mirrors
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In this paper, optimized Gires-Tournois mirrors were designed. The mirror structure was composed of 38 alternating Ta2O5 and SiO2 layers and could be regarded as two sections: high-reflectivity section consisted of a series of quarter-wavelength optical thickness stack and negative-dispersion section consisted of only 13 layers. The designed mirrors exhibit the desired performance. These mirrors were fabricated by use of ion beam sputtering. By use of such Gires-Tournois mirrors, dispersion of mode-locked fetosecond Ti:sapphire laser was compensated and 32fs pulse was obtained.
Study on the test of laser-induced damage threshold of multilayer dielectric gratings
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Multi-layer dielectric gratings (MDG) have been more and more used in the chirped-pulse amplification (CPA) system because of its higher diffraction efficiencies and higher damage threshold, which is compared with metallic gratings. Design parameter of multi-layer dielectric and gratings are both given. Laser-induced damage threshold (LIDT) of MDG has been test by employing 1-on-1 methods. The result is 3.24J/cm2 at 1064nm and 12ns pulselength (51.2° incidence). The mechanics of damage is also discussed in several ways.
The simulation of growth process of thin film on nonplanar substrate
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In (2+1) dimension, growth process of thin film on non-planar substrate in Kuramoto-Sivashinsky (K-S) model is studied with the numerical simulation approach. 15×15 semi-ellipsoids arranged orderly on the surface of substrate are used to represent initial rough surface of substrate. The results show that at the initial stage of growth process, the interface width constantly decreases with the growth time, then it reaches minimum. However, with the increase of growth time, the granules of different sizes distributes evenly on the surface of thin film. Whereafter the size of granules and the interface width gradually increase with the growth time, and the surface of thin film presents fractal properties.
Preparation of CoSi2 using microwave hydrogen plasma annealing
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Microwave hydrogen plasma annealing of sputter-deposited cobalt films on Si(100) substrate was utilized to form CoSi2 films which were characterized utilizing X-ray diffraction(XRD), Auger electron spectra(AES) sputter depth profile and cross-sectional Field Emission Scanning Electron Microscope (FESEM). Polycrystalline CoSi2, dominated by components with (111), was grown at the annealing temperature 600°C whereas microwave hydrogen plasma annealing at 750°C made components with (100) dominated. Moreover, it speculates that microwave anneal which promote Co atoms diffusion into Si substrate for nano-meter cobalt film during microwave anneal.
Charge collection properties of 1x128 array radiation detector based on CVD diamond film
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CVD diamond film has many excellent features, which promotes its potential application in radiation detection. In this paper, one kind of 1x128 array detector was developed by using a free-standing (100) textured CVD diamond film with a thickness of 300µm. The charge collection efficiencies (η) and distances (d) of the detector were investigated by using 241Am α particles (5.5MeV), 60Co γ-rays (1.25MeV), 55Fe X-rays (5.9KeV), resulting that the CVD diamond detector boasts high η (>38%) and d (>115µm), among which the η and d of X-ray reaches 41.70% and 125µm, respectively.
Optimization for the growth of CVD diamond on Al2O3 and the response to alpha particle irradiation
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A diamond film was grown on alumina ceramic by micro-wave plasma chemical vapor deposition (MPCVD) and was fabricated into an interdigited alpha-particle detector. By optimizing growth parameters in MPCVD, we found that under the conditions with carbon source (alcohol/hydrogen) concentration in 0.8% and deposition temperature at 850°C, the least content of sp2 and the best quality of diamond film could be obtained. Photocurrent under α-particle irradiation was in the range of 10-5~10-4A within one hundred voltages, and dark current was about 10-9~10-8A.
Effects of deposition conditions and annealing process on the infrared optical properties of diamond films grown by MPCVD
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The effects of deposition conditions and annealing process on the optical properties of diamond films on silicon substrate grown by MPCVD method are investigated by infrared spectroscopic ellipsometry (2.5-12.5μm). Results indicate that the low nucleation temperature will be in favor of decreasing the infrared absorption at 3.5μm. The refractive index n of diamond films deposited under higher growth temperature will fluctuate weakly. After annealing in N2 atmosphere an obvious improvement of the infrared optical properties is also found. After annealing the value of k was about 10-12~10-15. However, for non-annealed diamond film, the value of k was about 10-3~10-14. After annealing the refractive index n increased and was close to that of single crystal Type IIa natural diamond.
Liquid nitrogen flowrate alarm system for MBE
Yongwei Sun,
Shuying Li,
Haiqiao Ni,
et al.
Show abstract
Liquid nitrogen is very important for MBE system. Most MBE systems use the liquid nitrogen to absorb the impurity molecules. If MBE cryoshroud is lack of liquid nitrogen, the pressure of the growth chamber will grow. This will affect the film quality. But too much liquid nitrogen is a waste. We have developed a liquid nitrogen flowrate alarm system to monitor the liquid nitrogen status in MBE cryoshroud. In this method, a temperature sensor is placed at the end of the cryoshroud. The temperature varies with changing of the liquid nitrogen status in cryoshroud. If the liquid nitrogen level in the cryoshroud is too low or too high, the LNFA will send out an alarm to warn the user to adjust the liquid nitrogen flowrate. In our experiments, we found this method works well, and the temperature responds sensitively. With the help of this system, people can view the liquid nitrogen status of the entire growth process. Compare with other method, it is very cheap.
Deposition of microcrystalline silicon thin films for solar cells by VHF-PECVD
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Intrinsic microcrystalline silicon has been deposited by very high frequency plasma enhanced chemical vapor deposition (VHF-PECVD) technique at different discharge powers and silane concentrations. The results of Raman evidently show that the transition of materials from amorphous to microcrystalline silicon with the discharge power from low to high. To fabricate microcrystalline silicon material, the lower SC needs lower power and the higher SC needs higher power. The results of photo thermal deflection (PDS) measurements also indicate that the high quality of microcrystalline silicon was fabricated because of the low 'sub-band’ absorption coefficient, which is generally associated with defect densities. In addition, the results of dark conductivity and photosensitivity also evidently proved that a number of high quality microcrystalline silicon could be deposited by the optimization of experimental parameters. The results of active energy also show that material deposited by us could be used to fabricate solar cells. Preliminary results on the devices are presented: efficiency of approximately 5.3% was reached for 1μm thick solar cells.
Structural and electrical properties of Nd- and V-modified bismuth titanate thin films by sol-gel processing
Jinrong Cheng,
Liang He,
Zhongyan Meng
Show abstract
In this paper, Nd- and V- modified Bi3.15Nd0.85Ti3O12 (BNT), Bi3.15Nd0.85Ti2.97V0.03O12 (BNTV) and Bi4Ti3O12 (BIT) thin films were prepared on platinized silicon substrates by a using sol-gel processing. X-ray diffraction (XRD) analysis revealed that a single-phase BIT-type structure with (00l) preferred orientation was obtained for BNT and BNTV thin films annealed at 700 °C for 2 hours. Scanning Electric Microscopy (SEM) images showed that BNT and BNTV thin films had round and rod like grains, with the size of around 200-400 nm. BNT and BNTV thin films revealed improved dielectric and ferroelectric properties relative to BIT thin films. For the 1.12 µm thick BNT thin films, the dielectric constant achieves 428 at 1kHz, the remnant polarization and coercive field are of 17 µC/cm2 and 100 kV/cm, respectively. BNT thin films remained excellent electrical strength under the field as high as 600 kV/cm.
Study on oriented 3D mesoporous silica thin film and nano magnetic grain assembly
Jian Cheng Zhang,
Qi Liang Ni,
Yue Shen,
et al.
Show abstract
Mesoporous silica thin films with the three-dimensional (3D) pore structure and regular channels have been prepared by dip- or spin-coating on substrates with using a triblock copolymer surfactant (F127) as a template. This paper studied the influences of the various conditions on some characteristics of films with the oriented pore by DTA (different thermal analysis), FTIR (Fourier-transform infrared), small- or wide-angle X-ray diffraction (SA-or WA-XRD) and high-resolution transmission electron microscopy (HRTEM)etc. The adsorption and desorption for N2(BET method) show that the film's specific surface area is about more 650m2/g and the pore channels size is about 3- 7 nm. This work also reported the influence of the array pore structure assembled with ferric group on magnetization process and showed that the coercive force and specific saturation magnetization of composite occurred in different performance as compared with the conventional magnetic materials.
Post-treating techniques of porous silicon thin flm
Ziqiang Zhu,
Yongfu Long,
Shaoqiang Chen,
et al.
Show abstract
An effective and simple novel technique for post-treating of PS films has been developed. The post treatment technique can avoid the cracking of PS films and enhance the stability, the surface smoothness and the mechanical intensity of the PS films, resulting in the expansion of application of the PS films.
Research on the fabrication of µc-Si and its incubation layer
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Research on the fabrication of μc-Si used as the active layer of TFT and the incubation-layer of μc-Si is presented in this paper. VHF-PECVD is used to fabricate μc-Si film since the μc-Si can be fabricated with a higher growth rate than RF-PECVD. The amorphous incubation-layer between the substrate and the μc-Si layer can be thinned effectively by increasing hydrogen dilution. In addition, to obtain good TFT performance, the growth rate should be appropriate resulting in relative large grain size.
Visible photoluminescence originated from various mechanisms during step-by-step annealing
Jiaxin Mei,
Yunjun Rui,
Ling Yang,
et al.
Show abstract
Light emission variated from violet-blue to red-infrared is observed from a-Si:/SiO2 multilayers during step by step annealing. The peak of photoluminescence (PL) changes in the range between 417nm and 750nm under excitation of 325nm light as a function of annealing temperature, which is strong enough to be observed by naked eyes. Combined with Fourier Transform Infrared (FTIR) measurements, the correlation of the red PL excited by 488nm Ar+ laser and the structural evolution during the step by step annealing is detailed studied. The origins of different PL bands and the role of hydrogen and oxygen in microstructures of a-Si:/SiO2 multilayers are discussed
20-nm linewidth nanoimprint mold prepared by selectively etched multilayer thin film
Yongjun Zhang,
Guanqi Han,
Xinfan Huang,
et al.
Show abstract
A novel method to prepare nanomolds is reported, which is using multilayer thin-film deposition technique. A-Si/SiNx multilayer thin film is deposited on Si substrate in the conventional plasma enhanced chemical vapour deposition (PECVD) system. Then the relievo structure of alternative strips and grooves can be obtained on the cleaved cross-section of multilayer thin film by selective etching process. The strips of the etched sample have smooth and vertical sidewalls with small roughness. Due to the slow deposition rate, the thickness of the sublayer, therefore the size of the strips and grooves can be controlled on the nanometer scale by altering deposition time. The smallest width we get by now is the 20nm strips and 20nm grooves.
SiCN and Ta/TaN barriers for Cu/ultra low-k integration in 0.13µm technology
Show abstract
Single damascene Cu lines using bi-layer Ta/TaN barrier with and without SiCN and plasma treatment for Cu-ultra low-k interconnect in 0.13μm technology have been investigated. It was found that the N2/H2 plasma treatment on the ULK surface before depositing barrier and Cu could reduce the line resistance significantly, but it also brought more surface defects on the sidewall and larger diffusion length. Compared with only Ta/TaN barrier layer structure, introduction of an additional SiCN layer could significantly improve the breakdown voltage, line to line leakage and thermal stability. This is because the thin SiCN layer not only effectively blocks diffusion of elements on both sides, but also significantly improves the mechanical property of the ultra low-k polymer.
The studies of room-temperature electrical resistivity of post-annealed LaNiO3-ð thin film on Si(100)/n by RF magnetron sputtering
Show abstract
Highly (100)-oriented LaNiO3-δ (LNO) thin film were grown on n-type Si(100) at substrate temperature 200°C with 40% oxygen partial pressure. The as-deposited LNO films are metallic and have a resistivity of ~9×10-4 mΩcm at room temperature (RT) and can be used as the bottom electrode for the fabrication of integrated ferroelectric capacitors on Si. A post-annealing process can decrease the RT resistivity to ~3×10-4 Ωcm at 700°C and yield crack at 800°C.
Effects of oxygen pressure on optical and crystal properties of ZnO thin films prepared by laser molecular beam epitaxy
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C-axis oriented ZnO thin films were epitaxially grown at 350°C on sapphire (0001) substrates by laser molecular beam epitaxy(L-MBE) with oxygen pressures of 1.1E-4Pa,1.8E-4Pa, 2.3E-4Pa,and 2.1E-3Pa. As oxygen pressure increases, the full-width at half maximum(FWHM) of X-ray diffraction(XRD) becomes smaller and the diffraction peak intensity for (0002) planes becomes more intense as well as the symmetry of the peak shape becomes improved. Photoluminescence (PL) spectra of all samples show two emissions of a strong UV near-bandedge(NBE) emission peak at approximately 377 nm and a weak green-yellow deep level emission around 520nm. The samples grown with higher oxygen pressure have higher intensities of luminescence at 377 nm and the ratio of UV emission to deep level emission intensities increases. Reflection high energy electron diffraction (RHEED) pattern of ZnO films changes from spotty pattern to streaky one step by step with higher oxygen pressure.
A V-shaped module technique for promoting generation photocurrent density of silicon solar cells
Jianming Li,
Ming Chong,
Xiaofeng Duan,
et al.
Show abstract
A V-shaped solar cell module consists of two tilted mono-crystalline cells [J. Li, China Patent No. 200410007708.6 (March, 2004)]. The angle included between the two tilted cells is 90 degrees. The two cells were fabricated by using polished silicon wafers. The scheme of both-side polished wafers has been proposed to reduce optical loss. Compared to solar cells in a planar way, the V-shaped structure enhances external quantum efficiency and leads to an increase of 15% in generation photocurrent density. The following three kinds of trapped photons are suggested to contribute to the increase: (1) infrared photons converted from visible photons due to a transformation mechanism, (2) photons reflected from top contact metal, and (3) a residual reflection which can not be eliminated by an antireflection coating.
Thin Film Applications
Silicon-based one-dimensional photonic crystal microcavity
Show abstract
The layer-by-layer method is employed to prepare a-SiNx:H microcavity structure in a Plasma Enhanced Chemical Vapor Deposition (PECVD) chamber. Measurements of transmittance spectrum of as-grown samples show that the transmittance resonant peak of a cavity mode at 750 nm is introduced into the band gap of one-dimensional photonic crystal distributed Bragg reflectors based on hydrogenated amorphous silicon nitride. Also the PL measurements of a-SiNx:H microcavities are performed. There is a well agreement between the transmittance spectra and the PL of microcavity samples. In order to clarify the microcavity effects on the bulk a-SiNx:H, the PL of a λ/2-thick layer of bulk a-SiNx:H obtained under the same experimental conditions is presented. By comparison, a dramatic narrowing of emission linewidth and enhancement of PL intensity is observed. The wide emission band with 208 nm is strongly narrowed to 17 nm, and the resonant enhancement of the peak PL intensity is about two orders of magnitude with respect to the emission of the λ/2-thick layer of bulk a-SiNx:H. A linewidth of Δλ=17 nm and a quality factor of Q=50 are achieved in our one-dimensional a-SiNx photonic crystal microcavities.
Photonic crystal slab made from porous silicon
Show abstract
The concept of photonic crystal (PC) was raised by E.Yablonovitch and S.John respectively in 1989. Since then on, photonic crystal made tremendous progress in the research and application. Photonic crystal is not some kind of new materials but periodic dielectric materials. We have designed, fabricated photonic crystal slab (PCS) based on porous silicon. These alternating dielectric porous silicon layers show a band gap in one direction. Incident light is reflected for colors of light in the band gap, so porous silicon photonic crystal slabs have high reflection in the range of band gap. By mean of electrochemical lift-off, the PCS could be removed from silicon substrate, and PC band gap could be observed clearly in the reflectivity spectra.
Investigation of electrical, structural, and optical properties of very thin oxide/a-Si:H/c-Si interfaces passivated by cyanide treatment
Emil Pincik,
Hikaru Kobayashi,
Stanislav Jurecka,
et al.
Show abstract
The paper deals with investigation of electrical, structural and optical properties of very thin oxide/a-Si:H interfaces passivated by chemical treatment by KCN and HCN solutions. The oxide layers were prepared by thermal, chemical and plasma or ion beam assisted oxidations. Interface properties were evaluated by charge version of deep level transient spectroscopy, C-V measurements, X-ray diffraction (in both Bragg-Brentano and grazing incidence modes), optical reflectance (based on genetic algorithm) and photoluminescence. Considerable interest was devoted to distribution of three dominant groups of a-Si:H defect states in the band gap of the semiconductor as well as their response to bias annealing and light soaking experiments. We will present also dominant result - increase of the efficiency of a-Si:H based solar cells after chemical treatment. Finally, we will present the chemical passivation and oxidization as promising techniques suitable for applications in the field of nanotechnology.
Formation of random laser action in ZnO thin films
S. F. Yu,
Eunice S. P. Leong,
S. P. Lau,
et al.
Show abstract
A review of recent work on random laser action in ZnO thin films is presented. Room-temperature ultraviolet lasing has been demonstrated in highly disordered ZnO film grown on (100) silicon substrate. The disordered gain media is achieved by post growth annealing of ZnO films and random arrays of ZnO nanorod embedded in ZnO epilayers. Irregular ZnO grains are found to occur through post-growth annealing of high-crystal-quality zinc oxide thin films and laser cavities are generated by closed-loop optical scattering from the lateral facets of the grains. In the case for ZnO nanorod arrays, the design of slab waveguide provides extra gain length and shorter scattering mean free path and leads to coherent random lasing. It is found that the lasing wavelength and linewidth of the zinc oxide random lasers under 355 nm optical excitation are around 390 nm and less than 0.4 nm, respectively. In addition, the dependence of the lasing threshold intensity on the excitation area has shown good agreement with the random laser theory.
Non-polarizing filter design
Hong Ji Qi,
R. J. Hong,
Kui Yi,
et al.
Show abstract
Using the birefringent properties of thin film, a non-polarizing design concept is presented in this paper. This concept can be applied to design non-polarizing band-pass and edge filters at oblique incidence.
The LIDT of Ta2O5/SiO2 narrow-band interference filters under different laser modes
Show abstract
The Laser-induced damage behavior of narrow-band interference filters was investigated with a Nd:YAG laser at 1064nm under single-pulse mode and free-running mode. The absorption measurement of such coatings had been performed by Surface Thermal Lensing (STL) technique. And the relationship between damage morphology and absorption under the two different laser modes had also been studied in detail. The explanation is given by the standing-wave distribution theory.
Control of p- and n-type conduction in ZnO films and properties of ZnO p-n homojunctions
Canyun Zhang,
Jiming Bian,
Xiao Min Li
Show abstract
ZnO has attracted considerable attention as a potential candidate for short-wavelength optoelectronic devices. How to realize p-type ZnO films and ZnO p-n junctions is the key step for application of ZnO-based devices. We report the growth and properties of p-type ZnO films by combination of nitrogen and indium (N-In) codoping method and ultrasonic spray pyrolysis technique. The controllability of conductivity type in ZnO based films can be realized by adjusting the deposition and doping parameters. A conversion from p-type conduction to n-type conduction in a range of temperature has been identified by the measurement of Seebeck and Hall-effect for the first time. The two-layer structured ZnO p-n homojunctions with good rectifying characteristics were successfully prepared by depositing undoped ZnO on N-In codoped ZnO film. These achievements indicate it should be possible to fabricate ZnO-based optoelectronic devices such as light-emitting diodes (LEDs) and laser diodes (LDs) in the near future.
Failure analysis of MEMS RF cantilevered beam switch
Show abstract
A surface MEMS miniature switch with the cantilevered arm has been made on low resistivity Si substrate. The switch was inserted into a time domain setup and their lifetimes have been characterized as a function of actuated voltage, demonstrating some relationship among lifetime and threshold voltage. The structure of MEMS RF switch is simulated by ANSYS software, doing some failure analysis and discussing difference comparing the experiment.
Design and simulation of uncooled bi-material infrared detector
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A new uncooled bi-material microcantilever detector is based on between bi-material large difference in thermal expansion and Young’s modulus, having light, low cost, high sensitivity to radiation, and very matching with silicon IC technologies. A 3D microcantilever detector model had been built and simulated by ANSYS thermal-stress coupled, and gained responses to IR radiation with temperature changes, contributing to maximum deflection of geometry size.
Low-loss microwave coplanar waveguides realized on low-resistivity silicon wafer
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A low-loss microwave Coplanar Waveguides (CPW) was fabricated on Porous Silicon (PS) substrate oxidated and coated with polyimide. The high frequency performance of PS/Oxidated PS (OPS) was observed through fabrication and measurement of CPW on N/P-type PS. The CPW loss was lowered to 0-7.5dB/1.2cm in 0-40GHZ in comparison with quartz and poly-Si/SiO2/high -resistivity Si, and some conclusions were drawn out.
Impact of diode facet reflectivity on the fiber grating external-cavity semiconductor laser
Qingyang Xu,
Shaowu Chen
Show abstract
The scattering matrix method is used to analyze the multiple reflection effect between the laser diode facet and the fiber grating facet by considering the fiber grating external cavity laser diode (FGECL) as a four-mirror cavity laser. When neglecting other important parameters such as butt-coupling distance between the diode and the fiber facets, coupling efficiency, external cavity length, it is shown that low reflectivity is not a crucial factor for the laser characteristics such as SMSR. Experimentally high SMSR fiber grating external cavity laser is fabricated with a relatively large residual facet reflectivity (about 1%), which is coincident with our simulation results.
Optimized inductor and low-pass filter with low substrate loss on OPS/PS interlayer
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Oxidized porous silicon/porous silicon (OPS/PS) has been introduced as a low-loss substrate for an on-chip LC low-pass filter (LPF). The LPF is optimally designed with midband insertion loss (MIL) of -4.5dB and nominal cutoff frequency at 900MHz. The fabrication of the LPF based OPS/PS is in prevailing CMOS process. Experiments show that the performance of the LPF has been greatly improved with MIL of -4.54dB that meets the designed value quite well. And in comparison with MIL of LPF on SiO2/Si (8Ω cm), MIL with the proposed interlayer is lowered by 8dB, which implies that the microwave loss resulting from the substrate part can be substantially suppressed by introducing OPS/PS.
Influence of annealing on the nanosecond laser damage resistance of the dielectric mirror coatings at 1064-nm prepared by IBS
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Laser induced damage of multilayer has been investigated at different annealing temperatures. Ta2O5/SiO2 dielectric mirror coatings for 1064nm were prepared by ion beam sputtering (IBS), and then annealed in air at 250 centigrade and 350 centigrade, respectively. The microstructure of the samples was characterized by X-Ray diffraction (XRD). Absorption of the multilayer was measured by surface thermal lensing (STL) technique. Single-shot laser-induced damage threshold (LIDT) was assessed using 1064 nm Q-switched pulsed laser at a pulse length of 12ns. It was found that the center wavelength shifted to a longer wavelength as the annealing temperature increased. However, the samples kept its non-crystalline structure even after annealing. The absorbance of the samples decreased after annealing. An obvious decrease of the single-shot laser-induced damage threshold was found after annealing. Optical microscopy was employed in mapping laser-induced damage morphology features after laser irradiation.
Absorption measurement for coatings using surface thermal lensing technique
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Two absorption measuring methods by a measurement system based on Surface Thermal Lensing theory (STL) are given. The measuring results of coatings indicate a deviation of 5ppm and the sensitivity is better than 10ppm.
Porous-silicon-based oligonucleotide chips
Li Shao,
Shaoqiang Chen,
Jian Zhang,
et al.
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A novel oligonucleotide chip with porous silicon / oxidized porous silicon (PS/OPS) as its substrate has been developed. The attachment rate and detection sensitivity were improved obviously due to enormous surface area of PS/OPS compared to the existing conventional techniques. No dependence of storage condition on the detection sensitivity is found (signals variation is within SD). Stability of the oligonucleotide chips is good.
Design of negative dispersion mirrors used in Ti:sapphire femtosecond lasers
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An useful design used for the dispersion compensation in Ti:sapphire femtosecond lasers is reported. It is composed of 40 alternating Ta2O5 and SiO2 layers. The first part, from layer 1 to layer 25, which have quarter-wave optical thickness serve as high reflectivity dielectric stack. The second part, from layer 26 to layer 40, whose thicknesses are obtained by computer optimization provide negative group delay dispersion. The mirror has continuous high reflectance from 720nm to 870nm and near-constant group delay dispersion of -40fs2 from 740nm to 850nm. After seven bounces, such mirror can compensate most group delay dispersion and part third order dispersion of 4-mm Ti:sapphire crystal.
The test of new-type MEMS ammonia-sensitive sensor
Lingjie Wang,
Jishen Lin
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The paper discusses the test of the new type MEMS ammonia sensitive sensor. The sensor has a MOS structure. The sensitivity and stability of the sensor was studied. The paper focuses on the influence of the thin film decorated on the gate. The experimental results showed that the sensor has a good sensitivity and selectivity, that’s because its gate is decorated by mixed metal thin film. And only when the thin film is between 10nm and 30nm, the sensor was most sensitive to NH3.
High-isolation contact switch in MEMS phase shifter
Wei Li,
Yanling Shi,
Jian Qing,
et al.
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The design, fabrication and testing of high-isolation contact MEMS switch using AlSi membrane on high-resistivity silicon substrates are described. Simulation result of the switch is analyzed and shows good performance. The measured results show that the isolation of the MEMS switch is better than -30dB at 0.05 - 5GHz. And it has not only low actuation voltage, but also the high reliability. So this contact MEMS switch can be widely used in MEMS phase shifters.
Analysis of the tunnel junction current
Rong-hui Guo,
Zhengping Zhao,
Miao Lu
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In recent years, the development of sub-micron devices has offered the opportunity to transport electric charge by the manipulation of individual electrons. This kind of devices is called single-electron devices (SED), which mainly consist of many tunnel junctions. These tunnel junctions are more like sandwich structure made of metal-insulator-metal or semiconductor-insulator-semiconductor. So to analyze the SED’s characteristics intensively, one must first understand the process of the electron tunneling through the tunnel junction. But some papers make use of the simple approximation in which the tunneling matrix element is often taken as an electron energy-independent constant; some nice characteristics are maybe lost. We concentrate in this paper on investigating the relation between the tunneling matrix element and the energy of the electron. Some important results will be got, the tunnel current will be calculated for typical potential barrier.
ZrO2 thin films deposited on various LiB3O5 substrates by electron beam evaporation
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ZrO2 thin films were deposited using an electron beam evaporation technique on two kinds of LiB3O5 (LBO) substrates having the surfaces prepared by cutting at specified crystalline orientations. The results tested by the spectrophotometer indicated that all films had optical anisotropy, which was attributed to the film microstructure with preferred orientation from GXRD (grazing X-ray diffraction) analysis. The film microstructure difference deposited on LBO substrates with different crystalline orientation resulted in film refractive index change, namely, the ZrO2 thin film with the m-(-212) preferred orientation had lower refractive index than that with the o-(130) preferred orientation.
Bond enhance of hydroxyapatite/silicon layers by introducing a porous silicon interlayer
Shaoqiang Chen,
Jianzhong Zhu,
Jian Zhang,
et al.
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Hydroxyapatite (HAP) nano-particles obtained by coprecipitate process are deposited on porous silicon substrates, after being annealed, HAP films connected tightly with porous silicon substrates. The resulted samples were investigated by XRD, AFM and SEM.
Formation of the copper nanoparticles in porous silicon by electroplating
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A cheap and simple method of depositing copper into porous silicon by cathode electroplating was described. The existence of cubic copper nano-particles (~30nm) into porous silicon matrix was verified by X-ray Diffraction and Scanning Electron Microscopy. The microcrystal size of porous silicon and strain between porous silicon and copper layer were discussed based on the Raman spectra.
Resolution enhancement in optical lithography using polarized film mask
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The influence of polarization on the image performance of optical lithography systems has been systematically investigated through comparing the image contrast and the process window with TE-polarization, TM-polarization and un-polarized light, respectively. The simulation results show that the TE-polarization imaging is possible to improve the image performance of optical lithography systems, especially for those systems with high numerical aperture. The effects of polarized-light imaging with a conventional masks and a polarized film mask were studied by carrying out series of experiments under the conditions: 436nm exposure wavelength, numerical aperture of 0.5 and partial-coherence factor of 0.2. It is found that the image quality of the L&S patterns with the polarized film mask is better than that of with the conventional mask and, 0.3 μm L&S patterns are obtained with the polarized film mask.
A new type of tachometer circuit based on series magneto-diode
Liang-Gong Wen
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A new type of series connected double-injection magneto-diode formed on a SOI substrate is designed. This new type of magneto-diode features a considerably high sensitivity in response to a certain change of the magnetic field around it and also has the ability to compensate the excursion caused by the fluctuation of the temperature nearby. Other than the discussion of the structure, sensitivity, and the principle of work about this new magneto-diode, a new type of tachometer circuit based on this kind of magneto-diode that features a desirable stabilization and a relatively high sensitivity and can distinguish phases is designed. This circuit can be used widely to monitor the flux of liquid in many circumstances.
Influence of experimental environment on the process of photo-assisted electrochemical etching process on silicon
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Photo-assisted electrochemical etching is a newly developed technology for the deep etching process in silicon. The principle for such a process is based on the dissolution of silicon in a diluted HF strongly depends on the distribution of holes injection, so existence of tips lead to the electrochemical etching process along the vertical direction of the wafers. In this paper, the current-voltage characteristic of etching process and influence of temperature on the process of photo-assisted electrochemical etching process on silicon has been reported. In detail, the relationship between etching current and bias voltage in deferent region and the related mechanism, how does temperature influence this current-voltage characteristic have been explored. It is demonstrated that low temperature process and proper bias voltage is critical for the uniformity of PAECE process.
Transfer bonding of thick silicon nitride film via split of porous silicon
X. Q. Bao,
Yan Fang Ding,
Yu Chen,
et al.
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In this paper, silicon nitride film, as thick as 1.1μm, was first deposited on porous silicon by plasma enhanced chemical vapor deposition (PECVD). No crack was detected, on the contrary of the case that is deposited on a single crystalline thin film. Such layer was bonded to a glass substrate via a media of optical epoxy. And finally, separation of such layer from the original silicon substrate via splitting of porous silicon was investigated and the transmission properties before and after transfer bonding process were investigated. It is shown that such a transfer bonding process can be a good solution to the attenuation problem in silicon based RF system.
Simulation of output voltage waveform on thin film magnetoresistive sensor
Yu Shi,
Huaiwu Zhang,
Yingli Liu,
et al.
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A novel design model based on slant multi-phase filter(SMPF)theory is presented. The output voltage waveform of magnetoresistive(MR) element is simulated, it is found that the slant angle can affect the output performance of the MR sensor obviously. When the ratio of MR element length to magnetic pole length is five, the decrease of the output is small in the region where the slant angle is from 0 to 5°, less than 20%.
Numerical analysis of pull-in voltage for contact MEMS switches in switched-line phase shifter application
Ling Jiang,
Yanling Shi,
Wei Li,
et al.
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This paper presents numerical analysis of pull-in voltage for contact microelectromechanical (MEMS) switch in switched-line phase shifter application. The contact MEMS switch consists of a fixed-fixed thin metal membrane called the “bridge” suspended over a broken center conductor of coplanar waveguide (CPW). The center conductor sandwiched by a pair of symmetrical off-center drive capacitors that form two electrostatic actuators. A lumped-model for two coupled parallel-plates actuators is applied to describe the electromechanical behavior and the pull-in phenomenon in the contact MEMS switch. And a static mechanical model including the residual stress effects is developed to provide the effective stiffness coefficient for the prediction of pull-in voltage in a contact MEMS switch with uniform bridge width. As a theoretical basis, lower pull-in voltage can be achieved by optimizations on structure and material of bridge.
Study on DC-contact MEMS switches
J. J. Chen,
H. Z. Wei,
M. L. Hu,
et al.
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This paper presents the design, fabrication and performance of a metal-to-metal contact shunt micro-electro-mechanical (MEMS) switch. The switch was composed of a fixed-fixed Al0.96Si0.04 alloy beam with two pull-down electrodes and a central dc-contact area. The switch was placed in an in-line configuration in a coplanar waveguide transmission line. The best RF performance shows insertion loss of less than 0.3dB and isolation of greater than 35dB for all frequencies up to 10 GHz.
Evaluation of the mechanical properties of the materials in MEMS using an optical profiler
Haifei Bao,
Deren Lu,
Minghao Zhao
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In this paper an optical method using an optical profiler to evaluate the mechanical properties of the materials in MEMS is presented. As an example, a kind of cantilever plate-mass structure is prepared and measured to determine Young’s modulus of single crystal silicon and the residual stress of the thermal oxide SiO2 on it. An accurate deflection along the surface of the cantilever plate due to the action of residual stress or gravity can be easily obtained. The resolutions of the deflection and the load can be expected to be better than 1 nm and 0.1 μN respectively. The Young’s modulus and the residual stress at 163Gpa and -280Mpa, respectively.
Laser conditioning of dielectric oxide mirror coatings at 1064 nm
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Laser conditioning effects of the dielectric oxide mirror coatings with different designs were investigated. Simple quarter-wave ZrO2:Y2O3/SiO2 mirrors and half-wave SiO2 over-coated ZrO2:Y2O3/SiO2 mirror coatings at 1064nm were fabricated by E-beam evaporation (EBE). The absorbance of the samples before and after laser conditioning was measured by surface thermal lensing (STL) technology and the defects density was detected under Nomarski microscope. The enhancement of the laser damage resistance was found after laser conditioning. The dependence of the laser conditioning on the coating design was also observed and the over-coated sample obtained greatest enhancement, whereas the absorbance of the samples did not change obviously.
Index-compatible design of multilayer film for MEMS-type variable optical attenuator
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The MEMS-type Fabry-Perot cavity is used widely in some kinds of tunable optical MEMS devices. In this paper, the index compatible problem of multi-layer optical film design of Fabry-Perot cavity in the variable optical attenuator (VOA) has been investigated, which is using the transport matrix of optical medium film theoretically. Based on our theoretical model and simulation, our design for the MEMS-type Fabry-Perot cavity has better advantage of the compatibility. At first, it can be adjusted for the different working mode. Secondly, the thickness of the multi-layer film can be restructured according the refractive index of the material available. Finally, it is a self-alignment system, which makes it quite favorable for fiber alignment and procedure of package.
Study on multi-quantum barriers for use in quantum well solar cells
Linzhang Wu,
Wei Tian,
Xiaotao Jiang
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Quantum well solar cells (QWSC) extend the photon absorption edge beyond that of its bulk by incorporation of quantum wells in the i-region of a p-i-n device. When used in a QWSC, multi-quantum barriers (MQBs) can prevent the photo-generated electrons in the quantum well from leaking into p-side, and is therefore intended for a new method to reduce the dark current and enhance the photocurrent. Here we report on the performances of the MQBs for use in QWSC by dark current and photoluminescence measurement. It is found that the leakage possibility of the photo-generated electrons in the QW into p-side and thus the dark current is suppressed for solar cell with MQB compared with that without MQB.
Relaxation mechanism of SiGe thin film on SOI substrate
Zengfeng Di,
Miao Zhang,
Weili Liu,
et al.
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A different annealing method for the Si/SiGe bilayer fabricated on SIMOX wafer is proposed. After annealing for a short time, the Si/SiGe bilayer relaxes via the gliding motion of dislocations in the Si layer exclusively, leaving the top SiGe layer relaxed and mostly dislocation free. In addition, Ge does not diffuse into the top Si layer of SOI substrate to assist in the relaxation of the structure at the highest annealing temperature. At low annealing temperature, SiO2 is not expected to be viscous, and so the strain ratio is reduced in a linear fashion between 600°C and 900°C. When the annealing temperature becomes higher (for instance, 1000°C that is 58.5% of its melting point of 1710°C), the oxide can flow and the Si/SiGe bilayer behaves like a constrained thin foil slipping on the oxide. In this case, the strain ratio is dramatically reduced.
The process of low-stress silicon nitride and the application in the fabrication of MEMS device
Hongtao He,
Yongqing Xu,
Yongjun Yang
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Silicon nitride (Si3N4) is an important thin film materials in the construction of micromachined devices that depend upon low stress thin films. This paper presents the methods to obtain desired low stress levels for use in micromachined devices. By analyzing the mechanism of the stress, we developed the processes by LPCVD, to achieve the quality levels in the applications of MEMS. And the results of this process allowed us to form a low stress film for the fabrications of micro cantilevers, and the applications in the micro mirrors in the MOEMS. At last, the results of the MEMS devices is presented.
An investigation of polymer-carbon black composite gas detectors
Xiaoxiang Sun,
Haifen Xie,
Qiudong Yang,
et al.
Show abstract
In this paper, we describe the development of novel chemical gas sensors. These sensors consist of sensitive films and interdigited microelectrodes. The sensitive films are made of insulating polymers mixed with conducting carbon black. Interdigitated microelectrodes made of gold are fabricated on the silicon by VLSI technology and packaged. With the deposition of different polymer films on the interdigitated electrodes, we can make various polymer-carbon black composites chemresistive gas microsensors. When the sensitive films are exposed to organic gases, these films will absorb the gases and swell, that is, the resistance of the films goes to increase. We test two kinds of microsensors exposed in the same concentrations of organic gases. By principle component analysis of responses of microsensors, it is clear that two kinds of the same concentration different gases can be easily discriminated.
Gas sensor based on nano ZSM-5 zeolite films for the nerve agent simulant dimethylmethylphosphonate detection
Haifen Xie,
Yu Ting,
Xiaoxiang Sun,
et al.
Show abstract
The piezoelectric sensor device coated with nanosize ZSM-5 zeolite films has beem fabricated. The Nerve agent simulant Dimethylmethylphosphonate has been tested with this piezoelectric sensor devices. The frequency shifts to time at 1 ppm, 5ppm and 20ppm DMMP are examined respectively. The minimum detection concentration of 1ppm DMMP has been obtained in the N2 at 293K. 1 ppm is lower than the EC50 concentration value (where EC50 is the airborne concentration sufficient to induce severe effects in 50% of those exposed for 30 min). The frequency sensitivity was found to be about 60HZ / ppm. The effect of acetone on the ZSM-5 zeolite film was also investigated for the selectivity test. Using principle component analysis (PCA), we can qualify and quantify these testing gases.
Investigation on Eu3+ -doped Gd2O3 sol-gel thin films
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In combination with pyrolysis processing, the smooth, transparent and dense Gd2O3:Eu3+ thin films have been prepared by sol-gel technique under the absence of inert atmosphere. Comparing with powder samples, there is a remarkable variation in the excitation spectrum of thin film, which indicates that the energy transfer between Gd2O3 host lattice and Eu3+ activator is more effective in film configuration. The results of emission spectra excited by UV indicate that the optimal concentration of Eu3+ is about 10 mol.%. The phenomenon of luminescence reduction was observed for the films annealed at 1000°C, which results from the phase transition of cubic to monoclinic structure. The emission spectrum under X-ray excitation is also presented.
Modification of Gd2O3:Eu3+ sol-gel luminescence films
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Europium-doped gadolinium oxide films were prepared by the sol-gel method and spin-coating technique. The emission spectra of the films were investigated under both UV and X-ray excitation. Three kinds of cross-linking agents (EG, PEG200 and PEG400) were added to increase the thickness of the films. The luminescence intensity and the thickness of different film indicated PEG200 was the best cross-linking agent among the three compounds. At the same time, UV assisted technique as well as thermal decomposition technique have been introduced to reduce the film forming period and to prepare high quality luminescence films, and they can accelerate the film deposition process extremely.
Replication of the nano-scale mold fabricated with focused ion beam
J. X. Gao,
M. B. Chan-Park,
D. Z. Xie,
et al.
Show abstract
Silicon mold fabricated with Focused Ion Beam lithography (FIB) was used to make silicone elastomer molds. The silicon mold is composed of lattice of holes which the diameter and depth are about 200 nm and 60 nm, respectively. The silicone elastomer material was then used to replicate slavery mold. Our study show the replication process with the elastomer mold had been performed successfully and the diameter of humps on the elastomer mold is near to that of holes on the master mold. But the height of humps in the elastomer mold is only 42 nm and it is different from the depth of holes in the master mold.
Research for polyimide as a sacrificial layer in MEMS device
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Polyimide has been an important sacrificial layer material in the MEMS switch. Polyimide can be spun and photographied on silicon substrate. NaOH liquid can etch and develop polyimide. Then it needs to cure. After MEMS switch are manufactured, polyimide must be removed. The different cure temperature and time impacts the character of polyimide. The experiment result shows that it is easy to remove and can be lithographed. So it is suitable for microwave device. In this paper, refers that polyimide can be etched by NaOH, O2 and CF4.
Structural and electrical properties of high-ĸ Al2O3-ZrO2 gate dielectrics on SOI substrate
Yan Fang Ding,
G. S. Ye,
N. L. Zhang,
et al.
Show abstract
With the rapid development of semiconductor technology, feature size of MOSFET devices is scaling down. In the meantime the scaling down of the layer thickness of the gate insulator (SiO2) in advanced MOS devices is expected to reach its fundamental limit. But tunneling current through gate dielectrics and reliability become serious problems. From the point of view of both gate leakage current limitation and the stability and reliability of devices, it is necessary to seek some novel high κ dielectrics for low power sub-100-nm MOS transistor, whose physical thickness is big enough to suppress the tunneling effect, while at the same time keeping and increasing their capacitance.