Proceedings Volume 5635

Nanophotonics, Nanostructure, and Nanometrology

Xing Zhu, Stephen Y. Chou, Yasuhiko Arakawa
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Proceedings Volume 5635

Nanophotonics, Nanostructure, and Nanometrology

Xing Zhu, Stephen Y. Chou, Yasuhiko Arakawa
View the digital version of this volume at SPIE Digital Libarary.

Volume Details

Date Published: 9 February 2005
Contents: 9 Sessions, 66 Papers, 0 Presentations
Conference: Photonics Asia 2004
Volume Number: 5635

Table of Contents

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Table of Contents

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  • Theory of Near-field Optics and Surface Plasmons
  • Near-field Optics and Nano Optics
  • Optical Interactions and Temporal Behavior at Nanometer Scale
  • Nanostructures
  • Nano Devices and Photonic Crystals
  • Spectroscopy of Nanostructures
  • Poster Session
  • Nanotechnology in Life Sciences
  • Nanometrology and Characterization
  • Poster Session
  • Optical Interactions and Temporal Behavior at Nanometer Scale
  • Poster Session
  • Nanostructures
  • Poster Session
Theory of Near-field Optics and Surface Plasmons
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Super-resolution near-field imaging on microfluidic structure
Pei Wang, Lin Tang, Dou-Guo Zhang, et al.
A new proposal for biological or microfluidic detection based on super-resolution near-field structure (Super-RENS) proposed by Tominaga is described. The mechanism of the near-field structure we proposed to image microfluid is very similar to near-field scanning optical microscope (NSOM). In this paper, we describe our simulation model and results of the electric field distribution in the near field zone and readout signals from the near-field structure to image microfluid. Calculations have demonstrated that the near-field structure can be applied in biomedicine to detect tracing element or image microfluid etc with a high spatial resolution beyond the diffraction limit.
Study on near-field optical imaging mechanism
Qing Zhou, Xing Zhu, Hong Dai
We present three-dimensional simulations of the image formation of microstructure in near-field optical microscopy with the three-dimensional finite-difference time-domain method (FDTD). First, we calculated the intensity distributions inside and outside and the flux densities for both the tapered and parabolic fiber probes used in near-field optical microscope and nanolithography. The calculating result shows that for different kinds of shape the intensity distributions in both probes are similar and present standing wave forms; but the amplitudes and locations of peaks of the standing waves are different from each other. The intensity outward parabolic probe is higher than that outward tapered probe. Then we computed the intensity distributions of the samples which are composed of different materials by different polarization illumination. Assuming an aperture-type probe in collection-mode near-field microscope, we compare the images produced from the sample composed of three dielectric blocks in nanometer at a distance of 25nm and 150nm, respectively, under constant-high-scanning mode along with the direction of the polarization of the illuminating light, with near-field distribution of the sample without probe. The results show that the probe disturbs the original field distribution of the sample. The received signal is different from the original field distribution of the sample. However the received signal contains high frequency information of the sample in near-field region. Due to probe-sample interaction, parts of evanescent field transform into propagation wave. Only the interaction between the probe and sample in the near field makes possible to probe the high-frequency components and achieve the super-resolution. Therefore, the detected resolution depends on an assembly of the tip size, shape of the tip, distance between tip and sample, relative position and material characteristics of both tip and sample. These results provide the basis for correct interpretation of experimental work.
Near-field Optics and Nano Optics
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Influence of probe tip size and incident light polarization on resolution in near-field scanning optical microscopy
Guiying Wang, Qinghua Wu, Zhizhan Xu
Using probe-sample interaction equations based on the dipole-self-consistent field theory, we studied influence of the probe tip size on resolution in near-field scanning optical microscopic system for different undulate protuberance size of the sample surface and distance from the probe to the sample surface. These parameters in the NSOM were all normalized by the probe tip size in our numerical calculation, consequently a new definition expression of NSOMs resolution was suggested. Furthermore we calculated and analyzed polarization influence of the incident light on the resolution. Using probe tip size to normalize another parameter in the calculation and analysis causes the some succinctness conclusions.
The numerical simulation of field enhancement in near-field scanning Raman microscopy
The combination of plasmon near-field scanning optical microscopy (PNSOM) and Raman spectroscopy named Near-field Scanning Raman Microscopy (SNRM) provides not only surface topography information but also chemical structural information of sample with nanometer spatial resolution, which are very important for a wide range of applications, such as the study of liquid sample, nanometer film sample, quantum dot, single molecules of biological samples and so on. But Raman scattering cross-section is too small to get Raman signal of nanometer structure, and surface enhancement Raman scattering (SERS) effect is the main technique to solve this problem. Local electric field distribution and the form of the hot spots are evaluated by the FDTD (finite difference time domain) method in SERS with respect to many kinds of models. As a result in this paper, (1) vast Raman enhancement factor of 1015 was obtained around the junction between the Ag ball (tip) and the Ag thin film (sample stage). (2) The enormous large electric field at the hot spots rapidly decays with increasing gap between the Ag ball and Ag thin film. In the process, we use the equivalent incident wave method to deal with the incident evanescent wave problem and a frequency-dependent finite-difference time-domain formulation ((FD)2 TD) to deal with the negative permittivity of Ag, and the validity of these two methods have been approved by references
Numerical simulation of a new photon scanning tunneling microscope probe scanning imaging
Photon Scanning Tunneling Microscope (PSTM) is a near-field optical microscope that can measure local optical properties with high resolution beyond the diffraction limit and was widely applied in practices in recent years. The resolution of PSTM, which mainly depends on the shape of the taper tip, is an important issue to be discussed in the application. In this paper, the near-field distribution around a new PSTM probe is simulated by the method of 3-D Finite-Difference Time-Domain (FDTD). In this model, a nanometric metallic pyramid is attached at the apex of the metal-coated probe. Considering the interaction between the sample and the probe tip, the near-field distribution in a section at certain height is plotted as a function of the various sample positions. In order to optimize the optical property of this kind of optic fiber probe tip, the influence of the parameters of the taper tip can also be studied. To understand the effect of the probe film and the metal tip, the electromagnetic field distribution in the vicinities of the sample and the fiber probe during the third period is plotted. Thus, these simulated results offer references for the selection of the probe shape in experiments.
Numerical simulation of evanescent Bessel beams and apodization of evanescent field in near-field optical virtual probe
A near-field optical virtual probe based on the principle of near-field evanescent wave interference can be used in optical data storage, nano-lithography, near-field imaging and optical manipulation etc. The best choice of evanescent wave interference is evanescent Bessel beams that have the characteristics of both propagating Bessel beams and evanescent wave. It is concluded that evanescent Bessel beams is an evanescent wave with the characteristics of diffraction free and radial polarization. These characteristics lead to several advantages in near-field optics: the focus of radially polarized light can be quite smaller than the one of linear polarized light used commonly and diffraction free can bring in constant intensity distribution in a certain range. Meanwhile, based on the concept of conventional apodization, the idea of apodization of evanescent field is proposed to overcome some disadvantages of evanescent Bessel beams, such as the big side lobe and spread of transversal intensity. In this paper, Finite Difference Time Domain (FDTD) method is adopted to simulate the evanescent Bessel beams. Several parameters are considered as variants changeable to get the different simulation results. The better performance of the side lobe suppression and the narrow spot size are discussed. This work may be important to the application of near-field optical virtual probe in the future.
Optical Interactions and Temporal Behavior at Nanometer Scale
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Propagation of nonparaxial Gaussian beams
Guoquan Zhou, Shaomin Wang
Based on the nonparaxial moment theory of light beam propagation, the propagation characteristics of nonparaxial scalar Gaussian beam, nonparaxial TEM and TE vector Gaussian beams have been investigated. The results reveal that both the transversal beam widths follow a simple hyperbolic law upon propagation. The analytical expressions of the beam propagation factor, beam waist and far field divergence angle are presented, respectively. Furthermore, the formulae can be very concise for highly nonparaxial cases. TE or TM polarization will result in different propagating features in the two transversal directions. The maximum transverse divergence angles of nonparaxial scalar and vector Gaussain beams are different, which indicates that nonparaxial scalar Gaussian beam is no longer approximate at subwavelength scales. When extending to the paraxial case, the results obtained are slightly different from the formerly paraxial ones. Moreover, in this case the beam propagation factor will always be greater than unity. This research also denotes some properties of subwavelength optics.
Nanostructures
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Silver nanoparticles by laser ablation
The fabrication of a designed arrangement of matter at the nano-scale level is a central goal of contemporary engineering endeavours. Silver nanoparticles synthesized by a laser ablation method in pure water are able to produce the aggregates, agglomerates and crystals due to condensed matter physics and chemistry. The stability of agglomerates and crystals is variable, depending on the composition of ensembles dominated by Ag2O and Ag respectively. The paper will present some fascinating nanostructures, such as films and vesicles.
Synthesis and microstructure of dot-, rod-, and tetrapod-shaped CdTe nanocrystals
Colloidal II-VI semiconductor nanocrystals (NCs) are of increasing interest because of their potential applications as optoelectronic, photochemical, and nonlinear optical materials as well as biological labeling. The electronic and optical properties of these semiconductor NCs are controlled by their size, shape, surface, and surrounding environment. The capability to systematically manipulate the size and shape of the NCs remains an important goal of modern material science and technology. In this paper, we report the synthesis of colloidal dot-, rod- and tetrapod-shaped CdTe nanocrystals (NCs). The obtained NCs are characterized by transmission electron microscopy, Raman and X-ray diffraction spectra. Both the dot- and rod-shaped NCs are of zinc-blende phase whereas the tetrapod-shaped NCs are a mixture of zinc blende and wurtzite structures. It is proposed that the concentration of stacking faults forming during NCs' growth plays an important role in the geometry of CdTe NCs.
La2/3(Ca1/3Sr2/3)1/3MnO3 films deposited with femtosecond and nanosecond lasers
Xi Zhang, Xiao Yuan, Changle Chen, et al.
In this paper, deposition of La2/3(Ca1/3Sr2/3)1/3MnO3 thin films with femtosecond high repetition rate laser (1kHz) and low repetition rate nanosecond KrF laser (several Hz) are described. The X-ray diffraction pattern shows that the film has crystal plane orientation (100) on the LAO substrate and epitaxtial single crystal structure, and the composition analysis shows that the atomic percentage of Sr and Ca in the film is in good agreement with the target composition. The characteristics of the resistance with temperature is discussed.
Analysis of problems in measurement of SiO2 nanoparticle by dynamic light scattering
Based on the analysis of Dynamic Light Scattering(DLS) technique, and toke the measurement of SiO2 particle (size from 200nm-1300nm) using BI-200SM Goniometer as an example, this paper discussed the factors and the effects brought by these factors on measurement result. The analyzed factors include: poly of particles, inversion algorithm, irradiate time of laser on particles, surrounding temperature and the kind of liquid. Some phenomena was observed, such as: the difference among results by different algorithms changed with the change of particles' poly, the measurement result increased slightly as time went on, the size of particles increased greatly as the temperature was increased, the scattering light intensity was been depressed badly and the liquid with particles appeared unusually transparent and clean when SiO2 particles were put into ethanol.
Nano Devices and Photonic Crystals
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Emission decay and lamb shift in photonic crystals
Motivated by the significant controversy between the two dispersion models and Weisskopf-Wigner approximation (WWA), for the first time to our knowledge, we introduce the position-dependent photon-atom interaction into the Green function method of the evolution operator and develop a universal theoretical treatment on spontaneous emission of atoms in photonic crystals (PCs). A position-sensitive generalized Lorentzian formulism (non-Lorentzian shape) for the decay of an excited atom in PCs is derived, an exact numerical method for calculating the local coupling strength, proportional to the photonic local density of state (LDOS), is presented. For weak interaction PCs with pseudo gaps, the generalized Lorentzian formulism may be reduced to the famous Lorentzian spectrum. In this case, we introduced a lifetime distribution function for an assembly of atoms and found that the lifetime distribution strongly depend on the spread configuration of these atoms in space, which clarifies successfully the tremendous discrepancy between different experiments. For the PCs with large full gaps, we found that the atomic position can fundamentally change the decay behavior of an excited atom: in strong interaction positions, the atomic decay is non-classical or exhibits an envelope-damped Rabi oscillation, while in weak interaction positions the WWA is valid. Recently, we also predicted giant Lamb shifts for hydrogen atoms in PCs, and revealed that in inhomogeneous electromagnetic environment, the dominant contribution to the Lamb shift comes from real photon emission, while the contribution from emission and reabsorption of virtual photon is negligible, in vast contrast with the case of free space where the virtual photon processes play a key role.
Optical spectroscopy of silicon-on-insulator waveguide photonic crystals
Michele Belotti, Matteo Galli, Daniele Bajoni, et al.
Photonic modes in 1-D and 2-D silicon-on-insulator photonic crystal waveguides periodic or containing line-defects, are fully explored by means of angle- and polarization-resolved micro-reflectance measurements. Both quasi-guided and truly guided photonic modes are probed with a frequency-wave vector range that is greatly expanded under attenuated total reflectance configuration. It is shown that the presence of a supercell repetition in the direction perpendicular to a line defect leads to the simultaneous excitation of defect and bulk modes folded in a reduced Brillouin zone. Consequently, the group-velocity dispersion of the defect modes corresponding to different polarizations of light can be fully determined. We show also that the measured dispersion is in good agreement with full 3D calculations based on expansion in the waveguide modes.
Fabrication of three-dimensional void photonic crystals using ultrafast-laser-driven microexplosion in a solid polymer material
Micron-sized void dots have been generated in a solidified resin by using ultrafast-laser driven micro-explosion method. Side view confocal images of the void dots show that the void dots are almost spherical. The diameter of the void dots can be controlled by adjusting the laser power and exposure time. Three-dimensional (3D) structures, stacked in the [100] lattice direction, of diamond, FCC and BCC lattices have been fabricated, respectively. Multi-order stop gaps are observed for all three different types of structures. The suppression rate of the first order gap can be up to 70% for diamond and FCC structures. The angle dependence of the bandgap properties of a diamond structure reveals that the observed first order gap shifts to the longer wavelength whereas the second gap shifts to the shorter wavelength as the angle of incidence increases. Such a sensitive angular dependence of the bandgap structure may find applications in photonic crystal superprisms.
High spatial resolution investigation of electroluminescence of InGaN/GaN multiple quantum wells by using scanning near-field optical microscopy and spectroscopy
The electro-luminescence (EL) properties of InGaN/GaN multiple quantum wells (MQWs) light emitting diodes (LEDs) with various emitting wavelength (purple, blue and green) were studied by scanning near-field optical microscope (SNOM). The high spatial resolution EL SNOM mappings and near-field spectra of the LEDs were acquired at various injection current conditions. The experiment shows that, though there are some common points, the EL properties of various LEDs are quite different. (i) The EL mappings show that the MQWs emission is spatially inhomogenous, which contain many islands like bright spots. (ii) The sizes of the bright spots are different ranging from 0.1 μm to 1μm, the LED with longer emitting wavelength has larger bright spots. (iii) The injection current dependences of the shape of the bright spots of various LEDs are different. (iv) The emission wavelengths of brighter spots are longer in the same LED. (v) Increasing the injection current, the full widths at half maximum (FWHM) of the EL spectra grow larger. With the same injection current, the green LED has larger FWHMs than the blue and purple ones. (vi) Increasing the injection current, the blue shift of the green LED is obviously (~60 meV), but those of the blue one and purple are negligible. The phenomena above suggest that, the self-organized In-rich regions play a key role in the emission of all the InGaN/GaN MQWs LEDs, though they have different influences on the emission properties of the three LEDs with various emission wavelengths. One possible explanation is that, in the blue and purple LEDs, because the size of the In-rich areas are small, the quantum confined Stark effect caused by the piezoelectric field is negligible; but in the green LED, the In-rich areas are larger, the quantum confined Stark effect is obvious which caused the blue shift phenomenon. And in all LEDs, the band filling effect makes the FWHMs of the emission spectra larger. The results also show that SNOM is a powerful tool to study the local light emission properties at nanometer scale.
Spectroscopy of Nanostructures
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Fabrication of soft nanoimprint stamps and polymer subwavelength gratings by spin coating techniques
Yoshiaki Kanamori, Emmanuel Roy, Yong Chen
We report on a fabrication technique of both soft nanoimprint stamps and sub-wavelength gratings (SWGs) by spin coating of a polymer solution on a silicon mold. One and two-dimensional grating structures of periods 200nm were first obtained by high-resolution electron beam lithography and reactive ion etching of a silicon wafer. Then, a solution of polymethyl methacrylate (PMMA) was spun coated on the etched silicon molds. After baking, a thin layer of polydimethylsiloxane (PDMS) was assembled with PMMA sheet and mounted on a glass carrier. Scanning electron microscopy images of the replicated samples show high quality features reproduced from the silicon mold. Since PMMA is transparent for visible and near-infrared wavelengths, the replicated subwavelength gratings are applicable for many kinds of optical devices. In addition, the fabricated structure can be used as soft nanoimprint stamps which provides clear advantages of large surface patterning. The optical properties of both two and one-dimensional SWGs have been studied theoretically based on rigorous coupled-wave analysis (RCWA). The measured transmittance of the replicated antireflection SWG agreed well with the theoretical calculations.
Optical properties of ZnO cone arrays and influence of annealing on optical properties of ZnO-Zn coaxial nanocables
Xinhai Han, Guanzhong Wang, Jiansheng Jie, et al.
The novel ZnO cone arrays with controllable morphology and ZnO-Zn coaxial nanocables have been synthesized by thermal evaporating metal Zn powders at low temperature of 570°C without a metal catalyst. The ZnO cone arrays were grown on the Si (100) substrates, and clear structure evolutions were observed using scanning electron microscopy: well-aligned ZnO nanocones, double-cones with growing head cones attached by stem cones, cones with straight hexagonal pillar were achieved as the distance between the source and the substrates increased. X-ray diffraction showed that all of the cone arrays grow along c-axis. Raman and photoluminescence spectra revealed that the optical properties of the buffer layer between the ZnO cone arrays and the silicon substrates are better than those of ZnO cone arrays. ZnO-Zn nanocables were achieved in the region down stream with a temperature of 300°C. The PL measurements of the ZnO-Zn nanocables reveal a UV peak at 382nm corresponding to the free exciton emission originating from the ZnO shells, while violet luminescence centered around 424 and 431 nm are observed after annealed in Ar and air, respectively. The growth mechanisms of the ZnO cone arrays and ZnO-Zn nanocables are proposed.
Waveguide bends from nanometric silica wires
Limin Tong, Jingyi Lou, Eric Mazur
We propose to use bent silica wires with nanometric diameters to guide light as optical waveguide bend. We bend silica wires with scanning tunneling microscope probes under an optical microscope, and wire bends with bending radius smaller than 5 μm are obtained. Light from a He-Ne laser is launched into and guided through the wire bends, measured bending loss of a single bend is on the order of 1 dB. Brief introductions to the optical wave guiding and elastic bending properties of silica wires are also provided. Comparing with waveguide bends based on photonic bandgap structures, the waveguide bends from silica nanometric wires show advantages of simple structure, small overall size, easy fabrication and wide useful spectral range, which make them potentially useful in the miniaturization of photonic devices.
Non-aqueous cathodic electrodeposition of large scale uniform ZnO and CdO nanowire arrays
Qingtao Wang, Guanzhong Wang, Jiansheng Jie, et al.
We fabricated ordered ZnO and nanowire arrays in anodic alumina membrane (AAM) by cathodic electrodeposition from a non-aqueous dimethylsulfoxide (DMSO) bath containing zinc chloride and dissolved oxygen. X-ray diffraction (XRD), high-resolution transmission electron microcsopy (HRTEM), and electron diffraction (ED) show that the ZnO nanowires are well crystallized with wurtzite structure. The morphologies and structure of the ZnO nanowires have been characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results demonstrate that the ZnO nanowires with diameters of about 60nm are uniformly embedded into the hexagonally ordered nanopores of anodic alumina membrane. A sharp ultraviolet emission at 383nm and visible broad emission bands around 592nm were observed from ZnO nanowire arrays. They originated from the near-band emission due to the recombination of bound excitons and deep level emission due to defects, respectively. The cathodic electrodeposition technique in DMSO is also extended to synthesize CdO nanowire arrays.
Poster Session
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Scanning probe microscope visualization of t-loop assembly by TRF2 in cells
En-Hua Cao, Xiao-Fe Guo, Ju-Jun Wang, et al.
Telomeres are essential nucleoprotein structure at the ends of all eukaryotic chromosomes. Our previous work demonstrated that mammalian telomeres were shown to end in a large t-loop structure in vitro and the formation of t-loops was dependent on the presence of TRF2. In this work, the telomere DNA and its complex of TRF2 in HeLa cells has been direct observed in the nanometer resolution regime by atomic force microscopy (AFM) and scanning near-field optical microscopy (SNOM). AFM images showed that the looped structures exited in cell extract containing TRF2, but it disappeared in the protein-deleted samples. When cells were pretreated by UV light plus psoralen, the looped structure could be observed in the protein-deleted samples. SNOM images further demonstrated TRF2 and p53 proteins in cell was bound at the loop junction. Above results suggest that the telomere t-loop structure by TRF2 play a important role in cell-senescence, and might signals p53 protein directly through association with the t-loop junction in cells.
Nanotechnology in Life Sciences
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Fabrication of functional material by using DNA-lipid complex and its optical property
Masahiro Wada, Yoshiharu Kagami, Naoya Ogata, et al.
We observed optical properties of organic fluorescence materials doped DNA-CTMA and PMMA. The quantum yield in DNA-CTMA was higher than in PMMA. Amplified spontaneous emission properties of dye-doped DNA-CTMA film at ambient temperature were investigated. The narrowing of line shape and amplified spontaneous emission dependence occur at the same intensity indicates that both effects are the results of light amplification. We discussed the lasing capability by interacting DNA-CTMA.
Ultrafast dynamics of electron and hole in ZnSe quantum dots in gel glasses
Junfang He, Minqiang Wang, Zhihui Luo, et al.
ZnSe/SiO2 silica gel glasses were prepared through a sol-gel process. A femtosecond transient absorption spectroscopy and a time-resolved photoluminescence spectroscopy were used to detect the electron and hole relaxation in the ZnSe QDs. In the case of excitation 3.76eV, the TA and PL spectra were detected. The results showed that two competing processes, electron-hole recombination and surface electron trapping, occur in 10~100 ps time scale and the holes on valance band decay in about 1 ps.
Function of plastic optical fiber composed of DNA compound
M. Ozaki, Yoshiharu Kagami, Masahiro Wada, et al.
DNA fibers were prepared by melt spinning method from DNA-CTMA powder. A hemicyanine dye, trans-4-{4-(dibutylamino)-styryl}-1-methylpyridinium iodide (DBASMPI) doped DNA-CTMA fiber with core diameter of 1 mm and dye concentration of 3.6 wt% was obtained by soaking it in an aqueous dye solution. Laser (532 nm) pumped amplified spontaneous emission (ASE) at 610 nm was observed in the dye-doped DNA-CTMA fiber. The ASE occurred at energy density 50 mW. The amplification of optical signals at 607 nm wavelength was confirmed. The results from ASE emphasize that DBASMPI doped DNA-CTMA fiber is appealing as a good candidate for optical amplifiers and superfluorescence sources in a variety of communication and sensor applications.
Nanometrology and Characterization
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The phenomena and nature of characterized nano-radiation
Shaomin Wang, Laigui Hu, Daomu Zhao, et al.
Laser-induced white light emission from nano-carbon as well as other nanostructured materials in vacuum is presented in this article. It is observed only when the excitation laser intensity is higher than a threshold value (103-106 W/cm2). For the semiconductor nano-materials such as a cadmium sulphide (CdS) nano-crystal, a deep UV emission is also captured besides the white light emission. Spectra show that the nano-CdS radiate the stronger deep UV light with peak wavelengths about 210 and 215 nm. According this, a strong deep UV emission with a concomitant second harmonic generation at room temperature is also observed in a normal InGaAs laser diode (LD) operating at 980 nm. The output power of the UV radiation is estimated approaching to 0.1 mW. Since the wavelengths of the UV emission from nano-CdS are a little shorter than those of the InGaAs LD. These make it possible to develop deep UV wavelength LDs by doping different semiconductor nano-materials into the active layers besides using the III-nitride compound and ZnO semiconductor materials.
A new method for measuring a small displacement by using the critical angle method and confocal technology
A new method for measuring a very small displacement is presented. The principles of the measurement are based on the critical angle method and confocal technology. It will increase the lateral and longitudinal resolutions higher than 0.3μm and 5nm, respectively, and the maximum displacement could be above 12μm. This optical structure could be applied to measure some messages for optical surface, bio-medical science, and nanotechnology in the future. The new technique has some merits, such as a simple and compact optical setup, high sensitivity, and high resolution.
Research on sub-macro-offset difference and microparticle geometrical structure affection for atomic force microscope
Ruogu Zhu, Yu Huang, Lei Zhu
The measuring error from inherent sub-macro-offset for Atomic Force Microscope (AFM) is first proposed and named as the sub-macro difference in this paper. We give various model suggestions of interchange, bridge, interface and 'Taji' picture (or image) etc. for sub-macro concept. The sub-macro difference mainly includes two categories, such as the static or dynamic difference and the similar or ratio difference that is in scale between macroscopic and microscopic dimension or and the nano dimension. Meanwhile it is also suggested that the concept of measurable limit or critical geometric dimension in fact exists in the interchange area or the interface of the determination and probability shape by means of analyzing those influence of micro-particle geometrical construction based on its quantum behaviors and current macro measuring knowledge and experience. We can further research on the effects of quantum operators on dimension similarly or ratio difference, and the caution of nonlinear measuring error due to transition, symmetry and nonlinear transformation with the help of those suppositions.
In situ study of corrosion with an atomic force microscope scanning in liquids
In this paper, a new type of AFM scanning in liquid is developed. It circumvents the limitations of scanning electron microscopy by working in-situ, facilitating real-time studies of iron corrosion. We briefly introduce the structure of the AFM probe, liquid cell, scanning and photoelectronic feedback control system for image scanning and processing in liquid. By using the AFM scanning in liquid, a process of metal corrosion in liquid circumstance can be observed and the real-time images of the sample surface were successfully gained. The results indicated that although corrosion generally appears to be a macroscopic phenomenon, it typically begins at the atomic or near atomic level. And the experiments also show that this system could avoid the effect of surface tension and vibration on AFM images and was not restricted by sample's size and weight. It is of high repeatability, reliable stability and ideal contrast for image acquisition, and has a resolution of better than 1nm, covering a scan range from 100 nm x 100 nm to 10 mm x 10 mm.
Nanoscanning method for high-density grating measurement
Hongxin Luo, Changhe Zhou
The high-density grating is routinely used in a wide variety of applications using optics. However usually it is hard to measure such gratings directly by using conventional methods such as stylus profilometer and scanning probe microscope (SPM) that might damage the grating due to its fragile surface. A novel nano-scanning method based on the Talbot effect for measurement of a high-density grating is described in this paper. This method takes the advantage of the Talbot self-imaging effect of a grating with the conventional scanning near-field optical microscopy (SNOM) technique for measurement of a high density grating in nanometer accuracy without causing any damage to the grating under test. The noteworthy advantages of this method are its simple structure, easy operation and fast measurement of the quality of the grating under test. Three different kinds of gratings are measured in our experiments and the result demonstrates that this method is effective for evaluation of a high-density grating approximatively.
Poster Session
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Nanostructure generation based on laser cooling and mechanical mask
Xian Zhong Chen, Ting Wen Xing, Jian Ping Shi, et al.
The basic principle and the overall scheme of a new technique for nanostructure fabarication are described, and experimental results are given. A thermal atomic beam effusing out of an oven is firstly collimated by a small aperture and then collimated to a high degree by a polarization gradient laser field. This well-collimated atomic beam is patterned by a mechanical mask, and nanostructures are generated by atomic deposition. SEM profiles of nanostructures have shown that the feature size of the structure can reach nanometer scale. Compared to other micro-lithographic techniques, this technique has many advantages such as low cost, high throughput, mass production, simple process etc.
Influence of the bandwidth of an acquisition system on the trap stiffness measurement
Zan Gong, Hongtao Chen, Shenghua Xu, et al.
The high precision calibration of optical trap stiffness is the foundation of the weak force measurement in optical tweezers system. And the accuracy of the trap stiffness measurement is limited by the bandwidth of the acquisition system. In this article, such an influence is analyzed and discussed. First, the power spectrum of the thermal motion of a trapped bead is analyzed and the true trap stiffness is compared with the stiffness measured by a limited bandwidth acquisition system. Then the stiffness measuring process is simulated using Monte Carlo method when thermal motion analysis method is used to measure the trap stiffness. It is demonstrated that the influence of the bandwidth is related to the trap stiffness and bead diameter. And that the measured trap stiffness is greater than the true value is also demonstrated when the bandwidth of the acquisition system is not sufficient.
Electromagnetic theory of surface-enhanced Raman scattering for binary silver grating with nanometer dimensions
Grating-type substrates with nanometer dimensions offer the possibility of enhancing the electromagnetic field close to surface. Binary silver grating has been used to investigate the Surface-enhanced Raman Scattering (SERS). This paper describes the electromagnetic theory of SERS effect on the surface of a binary silver grating with nanometer dimension and discusses the TM-polarized incident light because surface plasmons excitation require this polarization . Laplacian's equation is given for this model in the grating region. We use the rigorous coupled wave analysis (RCWA) to solve the Maxwell differential equations in the grating region . The consideration of optimum incident angles for different gratings is also shown by analyzing the surface plasmon (SP) excitation . SERS enhancement factor is considered for binary grating with respect to the influence of angle incidence, grating depth and ratio of grating ridge width to grating period on both surface plasmon and SERS enhancement factor. Compared with the other SERS surface models, such as the isolated spheres model and other irregular models, this one-dimension regular model allows more quantitative estimates of the surface structures for the SERS effect.
Optical Interactions and Temporal Behavior at Nanometer Scale
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AFM imaging of proteus species
Shi Pan, Wei Sun, Lingfeng Song, et al.
With the fast development of scanning probe microscope, especially atomic force microscope (AFM), an imaging tool for life sciences researches is provided. Biological species imaging is one of the fundamental studies in life sciences, so it becomes one of the most important applications of AFM imaging. In this paper, AFM images of proteus species separately by contact-mode and intermittent-contact MacMode are obtained and investigated, and also are compared with its image of scanning electron microscope (SEM). Note that flagella are presented in SEM image while no evidence of flagella is observed when proteus species were imaged in AFM. This difference may be having something to do with sample preparation. The other possibility of this difference is that the proteus species which imaged was immature. Moreover, the images by MacMode in liquid medium show the outer surface of proteus species is smooth while the images by contact-mode in air show folding of the surface. The latter has clearly greater resolution than the former.
Poster Session
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Multiple Scattering Effects of Ag Particles in Super-Resolution Near-field Structure
Ruo Jian Zhu, Jia Wang, Ding Rong Ou, et al.
Random Ag-SiN films consisting of random small Ag particles embedded in a SiN thin film were deposited by radiant-frequency magnetron sputtering. Specimens orderly comprising a random Ag-SiN film and an optical phase change recording layer were exposed to a focused laser beam. It showed that, with a random Ag-SiN layer deposited above the recording layer, the ablation of the recording layer occurred much faster and under much lower power than that of a single recording layer, which verified the local field enhancement of multiple scattering effects of the Ag particles. Finite Difference Time Domain (FDTD) calculation of a sandwiched structure consisting of ZnS-SiO2(130nm)/AgOx(20nm)/ZnS-SiO2(40nm) under a Gaussian beam irradiation has been carried out to simulate the near-field distribution in the structure. Near-field optical data storage adopting a Super-Resolution Near-field Structure (Super-RENS) usually utilizes similar films structure mentioned above to achieve super resolution storage density while getting a high Carrier to Noise Ratio (CNR) at the same time. Many recent works have reported that small Ag particles were formed in the AgOx film after converging laser irradiation onto the sandwiched structure. Here, another FDTD calculation was done to simulate the same model except for that small Ag particles were modeled in the AgOx film in the center region of the incident laser spot. The results showed a huge local near-field enhancement, which indicates that, if the structure full of such small Ag particles are formed in a tiny region beyond the optical diffraction limit, the optical recording and readout out density would be improved as well as a high CNR level achieved due to the multiple scattering of the Ag particles.
Design and analysis of bow tie aperture with strong near-field enhancement effect
Jiying Xu, Jia Wang, Qian Tian
In this paper the near-field distributions of bow-tie apertures in visible range are characterized by the method of 3D finite-difference time-domain (FDTD). The numerical simulation results reveal theoretically the relation of field enhancement effect of bow-tie aperture and its several parameters including tip angle, aperture size and film thickness. For the bow-tie aperture with a certain tip angle, the metallic film's thickness can be firstly determined at its resonant peak, and then the aperture size can be determined at a tradeoff between the field enhancement and the field distribution. The calculation results of the transformed bow-tie apertures indicate that the transformation at tip angle will bring an obvious change to light field distribution. The bow-tie aperture can be directly used as an exit aperture of a very small aperture laser (VSAL) or as an unattached shield, to produce a sub-wavelength light source with high transmission. It is possible to be used in near field super-resolution imaging, high-density optical data storage, nano-photolithograhy and so on.
Near-field Raman spectral measurement of monocrystalline silicon by apertureless SNOM in feflection geometry
Xiaobin Wu, Yang Wang, Jia Wang, et al.
The combination of scanning near field optical microscopy (SNOM) and Raman spectroscopy provides specific spectra information with nanometer spatial resolution beyond the diffraction limit, which has a wide range of potential applications and can help to understand the interactions between light and matter in nanometer scale. In this paper, a near-field Raman spectroscopy experimental setup has been developed by using an apertureless SNOM system. An Ar+ laser (514nm ) is focused at an angle onto the sample surface. The metallized tip is an Au-layer-coated cantilever of an atomic force microscopy and working in the contact mode. The near field Raman spectra signal can be detected when the tip approached the sample surface. In addition, the apertureless SNOM appears to have greater potential resolution than aperture-type SNOM system. Furthermore, the reflection geometry employed in this experiment allows no need for specific sample preparation, making near field spectrum study a reality for any samples. The reflected near field Raman spectra signal is collected by a microscope objective. Finally, the near field Raman spectra of monocrystalline silicon are presented.
Optical spectroscopy of Ag-SiO2 nanocomposite coatings
Qiantao Li, Changxin Xiong, He Feng, et al.
In present work, Ag-SiO2 nano-composite coatings with Ag/Si=0.01~0.10(atom ratio) on soda-lime-silicate glasses have been prepared by sol-gel method. The optical absorption (OA) and photoluminescence (PL) spectroscopy of the coatings have been studied. The photoluminescence properties and mechanisms of samples, excited with 228nm and 325nm, have been discussed. The results indicate that the photoluminescence mostly associate with silver, which are in different chemical states. Excited with 228nm, the emission bands centered at about 365nm and 460nm originate from the electron transitions of 1D21S0 and 3D→1S0 in Ag+ respectively. Excited with 325nm, the emissions bands of 350~500nm and 640~690nm due to the silver clusters (Ag2+, Ag3+, etc.) and silver nanoparticles respectively. The presence of the silver nanoparticles gives a yellow color to the coatings, which show the well-know absorption band at about 400nm results from surface plasmon resonance. The XPS and TEM results show that the heat-treatment temperature, the Ag/Si ratio can influence chemical states of silver and can regulate the size, amount and distribution of silver nanaparticles in the matrix, then influence the optical properties.
Current detection during tip-induced anodic oxidation of titanium by atomic force microscope
Titanium film with about 3nm thickness is deposited on SiO2-Si substrate with dual facing targets sputtering method. Nano-oxidation lines are fabricated on this Ti film with various biased voltages and for the first time, current monitoring is performed during the oxidation process using a contact-mode AFM. In the cases of all lines, a flow of current began immediately when the biased voltage was applied and it kept almost unchanged as each of the oxide line was growing. The level of detected currents during the fabrication of oxide lines on Ti film is in the microampere (μA) level. The detected currents increase linearly with the biased voltages, which indicates that the detected current is mainly tunneling current. Thus, the process of nano-oxidation of Ti film is controlled either by the tunneling of electrons or holes through the Ti/water interface.
Theoretical calculation of quantum-confined stark effect in InAs/GaAs self-assembled quantum dots
A recent experiment on Stark effect spectroscopy in self-assembled quantum dots (SADs) has demonstrated the existence of an inverted electron-hole alignment due to the presence of gallium diffusion in InAs SADs and has established a relation between the Stark shift and the vertical electron-hole separation. The theoretical interpretation of these experimental results is based on the assumption that the applied electric field can be treated by the second-order perturbation theory, which results in a quadratical dependence of the transition energy on the applied electric field. While this relation is well satisfied in many quantum systems including single SADs and quantum well structures. But this relation is not valid for vertically coupled SAD structures, the asymmetric Stark shift of experimental measurement has shown existence of built-in dipole moment in InAs/GaAs QDs. Here we present a theoretical investigation of the factors influencing the sign and magnitude of the built-in dipole moment in realistic QD structures, including cubical, pyramidal and truncated pyramidal shape. The comparable results gave a reasonable interpretation for the experimental results. Our calculations consist of two basic steps. First, the strain is calculated for particular dot geometry with Green function methods. Second, the single-electron states are calculated using an electronic Hamiltonian, which depends on the strain. The computed states can then be used to determine various quantities, such as optical transition strengths, or exciton binding energies. In the article, we use Green function for the strain calculation, and plane-waves expansion in the envelope function approximation for the electronic structure calculations. The theoretical results agree well with the available experimental data. Our calculated results are useful for the application of QDs to photoelectric devices.
Analysis of near-field of diffractive gratings used in inertial confinement fusion driver
Diffractive gratings, such as 1 grating and beam sampling grating (BSG), are used in the inertial confinement fusion (ICF) driver because of their high diffractive efficiency. Under high power laser condition, it demands that near fields of the diffractive gratings, mainly affected by input laser energy and beam modulation, must be less than their damage threshold, otherwise the diffractive gratings will be damaged. In this paper, Fourier modal method based on the rigorous electromagnetic theory is introduced to rapidly and accurately analyze the distribution of near fields of the diffractive gratings. Its physical concept is clear and concise, and computation cost is small. Through numerical simulation, it indicates that the results calculated by Fourier modal method are accurate and effective, compared with those calculated by other method. The near fields of 1 grating used in final optical system of ICF driver are obtained. In addition, fabrication errors effects on the near field modulation are simulated. It shows that the sidewall slope errors are the main cause of optical field modulation. With theoretical analysis and numerical simulation, it is useful to understand mechanism of damage and help how to control fabrication process errors of the optical elements used in the optical system of ICF.
Investigation on long-range nanometer resolution grating moiré interferometer
Xingchun Chu, Haibao Lu, Tinzheng Chen, et al.
A moiré interferometer system based on single metrology grating (SMG) that can achieve nanometer resolution is presented. By properly selecting the diffraction beam, different resolution can be realized with different diffracting orders. The measuring principle is described in detail. A new moiré fringes subdividing method is developed. This method can accurately deal with input signals which deviate from the orthogonal state by dynamically tracing the joints of input signals. So the stringent requirement for orthogonality of input signals is loosen. With the combination of the SMG and new subdividing method, the system can easily achieve nanometer resolution. A displacement measuring system, which resolution is 1nm and measure range is 400mm, is set up. And the experiment results of the system are given. It shows that the system has better anti-jamming ability to the orthogonal error of input signals than conventional systems.
The simulation of the surface plasmon polaritons propagation on curved metal-dielectric interface
Lin Tang, Dou-Guo Zhang, Xiao-Jin Jiao, et al.
The SPPs propagation on curved metal-dielectric interface is simulated by FDTD(finite-difference time-domain) method. The propagation loss, the transmittance and the reflection coefficients of SPPs on curved metal-dielectric interface with different radius of curvature is presented. The results shows the radiation loss is the key factor for the SPPs propagation when the propagation area is the same order as the wavelength, and the reflection coefficient is so small that it is ignorable. The critical situation when the radius is zero is also analyzed and the reflection coefficient is much larger than the former situation; for the transmittance, different electronic field components play different roles.
The experimental study of super-smooth surface processing technology for optical glass and sapphire component
Chijuan Li, Jingling Xiao
This paper describes the super smooth surface optical processing methods for optical glass and sapphire components. The super smooth surfaces of optical glass through BFP (Bowl-Feed Polishing) method and sapphire through CMP (Chemo-Mechanical Polishing) method are produced respectively. Microstructures of each processing steps are measured through non-contact method with Zygo NV5022s. Finally, the experimental results are given: the roughness of both optical glass and sapphire component is around 0.5nm (rms or Ra).
The role of surface plasmon polaritons in the transmission of the light through different periodic structures in the metal film
The general role of the surface plasmons in the transmission of the metallic grating with narrow slits has been numerical described using the finite difference time domain method. Different parameters of grating have been used in the numerical simulation. It is concluded that whether the transmission peak of the SP resonance emerges or not does not depend on the SP travelling on the grating surface. The grating depth and the width of slit really give a dominant influence on the energy transmission for the SP resonance.
Preparation and characterization of ferroelectric inverse opal via a sol-gel process
Su Huang, Ai-Dong Li, Yuan Gao, et al.
Ferroelectric inverse opals are promising in making tunable photonic crystals. In this work, inverse opal photonic crystals of several ferroelectric materials such as (Pb1-xLax)(Zr1-yTiy)O3 (PLZT), SrxBa1-xNb2O6 (SBN) and PbTiO3 were prepared respectively by a sol-gel procedure. Synthetic opals of monodisperse submicrometer polystyrene (PS) spheres were used as the templates and precursor solutions were infiltrated into the interstices of the templates. The templates were removed by the following calcination process, which also realized the crystallization. Annealing process was optimized for each ferroelectric material. A scanning electron microscopy was used to observe the pattern of the inverse opals. XRD results proved that they were in desired ferroelectric phase respectively. The final samples were well ordered in all 3 dimensions within small domains. The average size of a single ordered domain in the SBN sample is about 20μm x 40μm. The size in PLZT and PbTiO3 samples is about 30μm x 50μm. Those domains distribute equably on an area of 2cm x 1cm on the substrates.
Numerical simulation of photon tunneling effects and the refractive index images of AF/PSTM
In this paper, three types of simulations will be performed using the three-dimensional finite difference time domain (3D-FDTD) method. First, we simulate the visualized interaction procedure of evanescent field coupling to the PSTM probe tip. Then, we show the variation in the field distribution above the sample as its refractive index and thickness are increased. Finally, we simulate the refractive index images based on the principle of separation of the refractive index image from the images of AF/PSTM for the realistic experiments. The numerical results are in good coincidence with the experimental results.
Two-dimensional photonic crystal polarization splitter
Mingyu Li, Peifu Gu, Jie Xing, et al.
A method is introduced to fabricate two-dimensional photonic crystal polarization splitter, which is based on the deposition of multiplayer films onto a grating. The plane-wave expansion method and the finite-difference time-domain method are used to calculate the band structure of this two-dimensional photonic crystal formed by a rectangular lattice of rectangular columns. After optimizing the thickness of each layer film, we find a large bandgap of TE. The theoretical relative bandwidth is 33.2%.
Influence of preparation technique on the microscopic structure and surface morphology of nanometer TiO2 thin films
Xiaoyun Hu, Jun Fan, Ting Li, et al.
Nanometer TiO2 thin films are prepared by a sol-gel method and the effects of preparation technique on the microstructure and surface morphology of the obtained materials are studied using X-ray Diffraction [XRD,IR spectrum[IR], UV-VIS spectrum [UV-VIS,AFM and X-ray photoelectron spectroscopy[XPS]. The results show that the TiO2 thin films are of anatase and rutile phase structures when annealed in a temperature range from 450°C to 600°C. When heated up to 700°C, the structure of TiO2 film changed into rutile completely. In the TiO2 thin films, there is some residual carbon from the starting organometallic components and a small amount of sodium ions diffused from the glass substrates. During heat-treatment, the absorption peak of water become weak gradually and the organic groups are disappeared completely at 500°C. Optimum film layers are obtained for the UV absorbance index. AFM result shows that the rough morphology of surface [RMS] of films is about 2-3nm or so.
Raman spectroscopy of annealed InAlAs quantum dots
Bin Wang, Xiaoxuan Xu, Yongchun Shu, et al.
Raman spectra of In0.65Al0.35As quantum dots (QDs) embedded between GaAlAs and GaP have been measured at room temperature. For the as-grown sample, in addition to the TO/LO modes from GaAs substrate, a weak broad peak appears from 165 cm-1 to 203 cm-1, corresponding to the interface mode of InAlAs QDs. The AlAs-like and GaP-like modes can be clearly seen at 382 cm-1. For the annealed samples, the AlAs and GaP-like modes disappeared, while the InAs-like modes become stronger, indicating strong intermixing between QDs and the matrix and the formation of uniform InGaAlAsP alloy.
Study of the spectra of silica colloidal crystals with assembled silver obtained from a photolysis method
The colorful artificial 3D silica colloidal crystals (opal) were prepared through self-assembly of silica spheres in the visible frequency range. We directly synthesized nano silver particles in the void of the silica artificial opal film using the photolysis of silver nitrate under UV light, nano silver particles were self-deposited around the surface of silica sphere. The shifts of the stop band of the artificial crystals after exposing different time under UV light were studied. Synthetic silica opal with three-dimensional (3D) structure is potentially useful for the development of diffractive optical devices, micro mechanical systems, and sensory elements because photonic band gaps obtained from self-assembled closely packed periodic structures.
Helicon wave plasma chemical vapor deposition of nanocrystalline silicon carbide films at low substrate temperature
Silicon carbide thin films have been deposited by helicon wave plasma enhanced chemical vapor deposition (HW-PECVD) technique under the conditions of variant deposition temperatures from 300 to 600°C. Silane, methane and hydrogen are used as reactive gas. The structural properties of the deposited films are characterized using Fourier transform infrared (FTIR), scan electron microscopy (SEM), transmission electron microscopy (TEM) and ultraviolet-visible optical absorption techniques. Detailed analysis of the FTIR spectra indicates that the onset of growing nanocrystalline SiC films at low substrate temperature is closed related with the high plasma ionization rate of helicon wave plasma and the condition of low working gas pressure and strong hydrogen dilution in experiment. The SEM and TEM measurements confirm that the structure of the deposited films is nanocrystalline SiC grains embedded in amorphous matrix and the size of the crystalline gains increases with substrate temperature.
Optical and tribological characteristic of nano-ZnO pressed disk
Linxing Shi, Xiangyin Li
The optical characteristics of nano-ZnO pressed disk are studied in this paper. Our study theoretically and experimentally introduced the related theories of the characteristic of laser signal reflected from nano-ZnO pressed disk, the effects of absorptance and transmissivity at different temperature field and roughness of surface. It has been found that nano-ZnO pressed disk has strong absorption peak at near 380 nm, but also the absorption peak decreases when disk's temperature increases. The surface topography and roughness properties of nano-ZnO pressed disk have been studied with atomic force microscope (AFM). Laser speckles are studied with semiconductor laser which wavelength is 650 nm. The tribological characteristics of ZnO nano-particles as lubricating oil additive were studied. The performances of antiwear and friction reduction in lubricating oil are markedly improved by adding ZnO nano-particles and dispersants together.
Optical absorption spectra analysis of silicon-rich hydrogenated amorphous silicon nitride thin films
Wei Yu, Yanbin Yang, Huijing Du, et al.
Silicon-rich hydrogenated silicon nitride thin films (a-SiNx:H) characterized with amorphous silicon cluster separations are deposited by helicon wave plasma-enhanced chemical vapor deposition technique. The optical absorption properties of the deposited films are obtained and analyzed from both light transmittance and reflectance measurements. A trend of blue shift of the exponential tail absorption region is observed with increasing nitrogen content x and the optical gap Eg, the Tauc coefficient B and the Urbach parameter EU have been discussed in terms of the compositional and structural characteristics of the deposited films. It is concluded that the separation of amorphous silicon particles from the a-SiNx:H matrices leads an increasing trend of more disorder microstructure presenting as the features of large EU and small B compared with normal films, especially, the blue shift of the optical absorption edge and the widening of the optical band gap correlated with a three-dimensional quantum confinement effect of amorphous silicon nano-particles is suggested for the films with higher x.
A wide-range metrology AFM and its applications
In view of the fact that the application field of a dual tunneling-unit scanning tunneling microscope (DTU-STM) was strongly limited by sample conductivity, a dual imaging unit atomic force microscope (DIU-AFM) was developed for wide-range nano-metrology. A periodic grating is employed as a reference sample. The DIU-AFM simultaneously scans the grating and a test sample by using one single XY scanner. Their images thus have the same lateral size, and the length of the test sample image can be precisely measured by counting the number of periodic features of the reference grating. We further developed a new method of implementing wide-range nano-metrology. By alternatively moving the XY scanner in the X direction using a step motor, a series of pairs of images are obtained and can be spliced into two wide-range reference and test ones, respectively. Again, the two spliced images are of the same size, and the length of test image can be measured based on the reference grating features. In this way, wide-range metrology with nanometer order accuracy is successfully realized.
A method to fabricate the bifunctional bent optical probes of AF/PSTM
We have developed an Atomic Force / Photon Scanning Tunneling Microscope (AF/PSTM) to eliminate the optical false image caused by topography of sample in PSTM. The key element of this system is bi-functional bent optical fiber probe, which can both be an optical cantilever and a device to collect the evanescent wave in near field of samples. In this paper, we derived a method to fabricate the bi-functional bent optical probes of AF/PSTM using communication optical fibers. The heated pulling combined with chemical etching method is proposed and developed. Fiber probes with an apex having a diameter smaller than 100nm could be produced with a controlled cone angles vary from 40 to 90 degrees. The back of the probe is finally coated with aluminum to enhance the reflection and with SiO2 to prevent Al film from oxidating in the atmosphere. This method is straightforward and fast. Using probes made with this method, the images of biology samples are obtained and the image separation is realized.
Development of optical phase shifter based on piezoelectric ceramic
The phase shifter is necessary in the optical phase-shifting measurement. At present the phase shifter commonly used is approximately divided into the penetrance-type and the reflection-type. In this paper, a reflection-type phase shifter made of piezoelectric ceramic stackup assemble is developed. The assemble are constituted of the flat piezoelectric ceramic with parallel connection circuit and inline structure. The communication between the computer and MCU is by RS232. The D/A converter controlled by the MCU outputs 0~10V voltage. Then the voltage is amplified to 0~400V DC voltage by the designed linear DC amplifier. When this voltage loads on the piezoelectric ceramic stackup assemble, the assemble will axially extend 0~5mm. In this paper, the connecting types for the mechanical construction and circuit of the piezoelectric ceramic stackup assemble, the driving power and the DC amplifier with high linearity are all introduced. The whole system developed is standardized by using phase-interfering Michelson. The standardization and the practical application indicates that this system has excellent linearity and precision repeatability.
Analysis of AFM vibrating nanotube tip imaging
ZengWen Xiao, Xuezeng Zhao
With the development of semiconductor technology, improving precision of linewidth measurement allows of no delay. Measured with atomic force microscope (AFM), linewidth uncertainty is affected most by its tip. The effect on linewidth measurement by vibrating tip top's track and lateral profile of carbon nanotube tip (CNT) is illuminated by simulation. The track is described by vibration model. The profile is drawn-out from the tip’s lateral image photographed by scanning electron microscope (SEM). According to the simulation results, the essential conditions that linewidth is measured with CNT are presented. Improving parameters of cantilever can decrease or eliminate the effect of track.
Random lasers emission from surface-corrugated waveguide
Qinghai Song, Lei Wang, Shumin Xiao, et al.
We report for the first time to our knowledge, the random laser emission from surface corrugated waveguides. Discrete lasing modes, super narrow spectral linewidth, and the existence of lasing threshold behavior have been observed. A theoretical model combining transfer matrix method and effective refractive index method was presented to explain the random lasing phenomena.
Study on measurement interaction force on living cell by atomic force microscopy
Yanxia Wang, Yanning Li, Xing Fu, et al.
A theoretical and experimental investigation of the force-distance relation in the case between a pyramidal tip and a cell is presented. The shape of the tip in use consists of a truncated pyramid covered by a spherical cap. The interaction force is computed the total interaction between macroscopic bodies. The experimental method is depicted in detail. The experimental results are comparison with the theory. The mechanical properties of the cell can be determined accurately and spatially well resolved from interaction force of tip-cell in AFM.
Plasmon localization and local field distribution of metal nanoparticles
Junying Zeng, Xiaoyan Zhang, Tao Zhou, et al.
We investigate the plasmon resonances of 100nm nanowires with a non-elliptical section (a triangular metal particle) using the finite difference time domain method (FDTD). By modeling the frequency dependent dielectric response of the triangular metal particle, we find the field distribution at the surface of these wires exhibits a dramatic enhancement, up to several tens times the incident field amplitude. In particular, the strongest electric field enhancement with the greatest confinement occurs for the excitations of modes localized at the corner of the metal triangular. Bulk modes excited in the triangular particle also produce enhancement although over a larger area and with significantly less enhancement than that of the localized modes. Adding a dipole at the corner of the triangular metal particle, the field distribution at the corner of these particles exhibits a more dramatic enhancement, up to several hundreds times. These strongly localized fields can provide an important mechanism for surface enhanced Raman scattering.
Surface-enhanced Raman scattering of biological molecules on mixed metal colloids
Jinghuai Fang, Yuan Li D.V.M., Yanyun Jin, et al.
Positively charged silver colloid and negatively gold colloid were prepared in aqueous solution for surface-enhanced Raman scattering (SERS) by the chemical reduction of metallic ions in aqueous solution with sodium borohydride solution in ice-cooled condition, respectively. SERS from glycine molecules in above mentioned colloidal systems were recorded respectively and compared with each other. The results show that the mixture of silver and gold colloids could form aggregation different from that of single silver colloid and gold colloid and bring about the favorable effect on SERS behavior for adsorbed glycine.
Research on surface modification of nano-zirconia
Wen Chen, Cun-Lin Zhang, Xiao-Yi Yang
The mechanisms about the aggregation and dispersibility of nano-zirconia were analyzed in detail. And nano-zirconia powders which were surface-modified with silane coupling reagent WD70 were prepared in order to disperse homogeneously in ethanol in this investigation. The grain size and grain phase of nano-zirconia were obtained by XRD. Research and characterization on the structure and surface characteristic of surface-modified nano-zirconia were achieved by XPS, TG-DSC, TEM and FT-IR. The results given by FT-IR and XPS showed WD70 was jointed on the surface of nano-zirconia through both physical adsorption and chemical binding after the de-methanol reaction between the methoxyl groups of WD70 and the hydroxy groups on the surface of nano-zirconia. And the corresponding model of surface-modified nano-zirconia was given. The images provided by TEM presented intuitionistic effect of surface modification on the dispersibility of nano-zirconia in ethanol. And TG-DSC analysis ascertained the amount of WD70 that was jointed on the surface of nano-zirconia and the amount was about 6.21 percent.
High-speed nanometer lapping photonics elements
This paper discusses some problems about nanometer lapping photonics elements. The solid abrasives high speed lapping method and the theory of lapping tool wearing uniformly are used in machining photonics elements. It makes workpiece machined surface roughness reach to Ra0.88nm, flatness reach 19nm. That not only realizes nanometer machining, but also realizes machining at high efficiency and low cost.
Present state and development of nanometrology
The development of micro-electronic has been entering the era of nano in advance, consequently, the measurement, metrology, trace and instrument calibration on nano scope must be up to the determined accuracy. Apart aside the traditional methods such as the aid of standard samples, the self-calibration of instrument is based on the 3D laser interference system with stabilized laser applied to SPM, which can also make the measurement result traceable to the primary standard of length unit directly. However, the complexity of instrument and the characteristic of sample make the elimination of error sources more difficult, so it is not enough to correct resolution just with methods above. The paper will introduce the statement and development of nanometrology and force on some original calibration methods.
Nanostructures
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Visualizing substructure of Ca2+ waves by total internal reflection fluorescence microscopy
Yongqiang Bai, Aihui Tang, Shiqiang Wang, et al.
Total internal reflection fluorescence microscope is a new optical microscopic system based on near-field optical theory. Its character of illumination by evanescent wave, together with the great signal-to-noise ratio and temporal resolution achieved by high quality CCD, allows us to analyze the spatiotemporal details of local Ca2+ dynamics within the nanoscale microdomain surrounding different Ca2+ channels. We have recently constructed a versatile objective TIRFM equipped with a high numerical aperture (NA=1.45) objective. Using fluo-4 as the Ca2+ indicator, we visualized the near-membrane profiles of Ca2+ waves and elementary Ca2+ sparks generated by Ca2+ release channels in rat ventricular myocytes. Different from those detected using conventional and confocal microscopy, Ca2+ waves observed with TIRFM exhibited fine inhomogenous substructures composed of fluctuating Ca2+ sparks. The anfractuous routes of spark recruitment suggested that the propagation of Ca2+ waves is much more complicated than previously imagined. We believe that TIRFM will provide a unique tool for dissecting the microscopic mechanisms of intracellular Ca2+ signaling.
Poster Session
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Modeling optical wave guiding in metal-coated silica nanowires
Jingyi Lou, Limin Tong, Zhizhen Ye
Based on the exact solution of Maxwell’s equations and numerical calculations, we have investigated the basic theoretical properties of metal-coated silica nanowires. Modal profile, field and power distributions, and conditions for surface plasmon excitation are studied. It shows that a thin layer of metal coat can influence the distribution of the electromagnetic field and enhance confinement ability of light power inside silica core due to its negative dielectric function, which may be favorable for reducing the size of wire waveguide for microphotonic applications.
A horizontal atomic force microscope and its applications
A new type of horizontal atomic force microscope (AFM) is developed for applications in nanotechnology. This article provides the basic principle and setup of the horizontal AFM. The light pressure of laser and the gravity exerting on the micro-cantilever was first conducted, conceiving a method to remove the effects of these factors on the interaction mechanism of atomic force and the performance of AFM. It has a horizontally designed probe unit and owns a particular path of optical beam deflection method for the measurement of cantilever’s displacement with its minimized structure. For the purpose of precise and effective imaging for different samples, we introduced a novel method to adjust the setpoint of imaging force and provided the calculative formula. A new feedback controlling theory and method of horizontal AFM was also advanced in order to develop an effective, steady and optimum feedback controlling system. Experiments show that the horizontal AFM is of high repeatability, reliable stability and ideal contrast for image acquisition. The horizontal and vertical resolutions of the system are 3 nm and 1 nm, respectively, with a maximum scan range of 10 mm´ 10 mm. These remarkable characteristics enable the AFM system to be widely applied in the fields of nanotechnology.