Proceedings Volume 3484

Lasers in Synthesis, Characterization, and Processing of Diamond

Vitali I. Konov, Victor G. Ralchenko
cover
Proceedings Volume 3484

Lasers in Synthesis, Characterization, and Processing of Diamond

Vitali I. Konov, Victor G. Ralchenko
View the digital version of this volume at SPIE Digital Libarary.

Volume Details

Date Published: 20 October 1998
Contents: 6 Sessions, 29 Papers, 0 Presentations
Conference: Lasers in Synthesis, Characterization, and Processing of Diamond 1997
Volume Number: 3484

Table of Contents

icon_mobile_dropdown

Table of Contents

All links to SPIE Proceedings will open in the SPIE Digital Library. external link icon
View Session icon_mobile_dropdown
  • Deposition
  • In-Situ Control
  • Spectroscopy
  • Processing
  • Applications
  • Thermal Properties
Deposition
icon_mobile_dropdown
Laser-driven plasma CVD of thin films
Vitali I. Konov, Alexander M. Prokhorov, S. A. Uglov, et al.
A novel technique for CVD synthesis of materials, that does not demand a vacuum chamber and provides high deposition rates, have been developed. It is based on CW CO2-laser maintenance of a stationary optical discharge in a gas stream, exhausting over a substrate into the air. Nano- and polycrystalline diamond films were deposited on tungsten substrates from atmospherics pressure Xe(Ar):H2:CH4 gas mixtures at flow rates 2 1/min. 2,5 kW CO2-laser focused beam produced plasma. Deposition area was about 1 cm2 and growth rates up to 30-50 micrometers /hour. Peculiarities and advantages of laser plasmatrons are discussed.
Deposition and laser damage tests of DLC coatings on silica optical fibers and plates
Serge V. Garnov, Victor G. Ralchenko, S. A. Uglov, et al.
We report on deposition and laser damage test of DLC coatings on silica plates and tip of 0.4 mm diameter fibers. The carbon films were produced by three techniques: (i) pulsed CO2 laser sputtering of glassy carbon targets in high vacuum; (ii) mono-energetic carbon ion beam deposition; and (iii) R.F. plasma deposition in benzene. Raman spectroscopy, ellipsometry and scratch tests were used to characterize structure, optical constants n and k, and adhesion of the films. The 20 ns pulses of a Q-switched YAG:Nd laser emitted at 1.06 micrometers were used to determine the laser damage threshold fluence, Wd, of the films. The R.F. plasma deposited coatings have demonstrated the highest values of Wd equals 18-22 J/cm2. A combination of small thickness, relatively low absorption, and good adhesion were the key to the success for these films. In spite of lower absorption the a-C films deposited by ion beam technique showed poorer resistance to laser shots because of insufficient adhesion. The a-C films produced by CO2 laser sputtering have shown very low damage thresholds because of high absorption. Attempts to grow polycrystalline diamond films on silica fibers are also described.
Synthesis of carbyne from amorphous line-chain carbon and pyrographite
M. B. Guseva, V. M. Babina, M. Boustie, et al.
Two types of carbon materials after the powerful laser influence were studied. First - low grade pyrolitic graphite, second - 10 micron film of the amorphous line- chain carbon. The film was prepared by the method of Ar ion assisted deposition of carbon plasma. The samples were irradiated by a 1.06 micro wavelength Nd laser in vacuum 0.3 Pa. The energy of the laser pulse was approximately 70 J, the duration 580 ps and intensity 440 GW/cm2. After the experiments the samples were examined by means of transmission electron microscopy. Auger and Raman spectroscopy. The formation of carbyne crystals with lattice parameters 'a' 0.516 and 0.533 nm were detected in the shocked samples. A small amount of nanodiamond was detected, too. An interesting feature is the formation of large carbyne crystals in pyrographite. Raman spectra of recovered materials exhibit strong peaks at the frequencies corresponding to the oscillations of carbon atoms in line- chain structures.
Chemical vapor deposition of diamond films on nonuniformly heated substrates
Mukhsin Kh. Ashurov, M. S. Saidov, T. M. Saliev
To observe the effect of temperature on the deposition processes polycrystalline diamond films were gown on the nonuniformly heated substrates by hot filament chemical vapor deposition technique using methanol and hydrogen gas mixture in quartz reactor. To provide nonuniformity of substrate temperature molybdenum pedestal was placed on the quartz tube, which removed heat from the substrate. p-type and silicon n-type and 6H silicon wafers were used as substrate. Polycrystalline diamond films with grain size of 1-3 micron were deposited.An applicability of diamond pyramid hardness tester for the preliminary examination of the diamond films is shown. Scanning electron micrographs and Raman spectrum of some films are presented.
Pulsed-laser-driven plasma CVD of CN/BN compound films
Vladimir G. Ageev, M. V. Ugarov, E. N. Loubnin, et al.
The deposition of boron nitride and carbon nitride films by laser-induced plasma CVD was performed for the first time. The composition and structure of films grown in different experimental conditions was studied by methods of Raman spectroscopy and x-ray photoelectron spectroscopy. It was found that high fractions of sp3 C-N bonding in CN films and hexagonal type B-N bonding in BN films can be produced by this method. All the synthesized films were amorphous. The prospective for the development of B-C-N based compounds deposition by laser plasma technique is discussed.
In-Situ Control
icon_mobile_dropdown
Use of resonance-enhanced multiphoton ionization (REMPI) for probing hydrogen atoms in diamond chemical vapor deposition using a hot filament reactor
Stephen A. Redman, Stephen R. Langford, Keith N. Rosser, et al.
We illustrate advantages of H atom multiphoton ionization spectroscopy, resonance enhanced at the two photon energy by the 2s1. 2S1/2 state, as a means of obtaining spatially resolved, relative H atom concentrations and gas temperature profiles within a hot filament CVD reactor, and investigating the way in which these parameters depend on process conditions.
Three-dimensional distributions of methyl density in a hot-filament CVD reactor: comparison with cavity ring-down spectroscopy measurements
Yuri A. Mankelevich, Nikolay V. Suetin
Developed 3D model of a hot-filament chemical vapor deposition reactor is used to reconstruct the methyl density spatial distributions and to describe reactor parameters dependencies of CH3 which have been measured, by others, using a line-of-sight optical technique called cavity ring- down spectroscopy (CRDS). In the model full set of transport equations taking into account the detailed gas-phase reaction mechanisms, molecular diffusion and thermodiffusion, catalytic hydrogen dissociation at the filament and surface kinetics at the substrate is numerically solved. The results of 3D and 2D model calculations are compared with the high sensitivity measurements of methyl radical absorbance at 231.9 nm by CRDS. Good quantitative agreement of experimental data and 3D model results, in contrast to 2D model calculations, was obtained. An importance of 3D effects for the species densities and gas temperature distributions is revealed.
Raman spectrometer for in-situ study of diamond growth in DC discharge plasma CVD reactor
Alexander N. Obraztsov, Igor Pavlovsky
A Raman spectrometer designed for the purpose of in-situ diagnostics of materials deposited in a gas discharge plasma under conditions of intense illumination from the discharge and heat radiation from a substrate is described. The characteristic feature of the spectrometer is the use of a pulsed Cu-vapor laser as the excitation source, along with the gated detection of the signal from a photomultiplier tube. The spectrometer is the fully PC-controlled system made on the base of a double grating monomchromator. The operation of the spectrometer is demonstrated in application to the study of processes of growth and modification of polycrystalline diamond films under d.c. discharge conditions. It is shown that in-situ Raman spectroscopy can be used for determination of the phase composition and the thickness of the deposited carbon films, and, also their temperature, internal stress, and changes of these parameters during the film growth.
Spectroscopy
icon_mobile_dropdown
Laser and emission spectroscopies for studying a diamond deposition MPACVD reactor
Alix Gicquel, Francois Silva, Marc Dubus, et al.
Correlations between some plasma characteristics and diamond ones are reported while changing the coupled action of some parameters: microwave power density, substrate temperature, and methane and nitrogen concentrations in the feed gas mixture. Based on this correlation, an interpretation for the formation of diamond films with a < 100 > texture associated with (100) faces morphology in presence of nitrogen is proposed.
Diamond: a material for laser spectroscopy
M. C. Castex, D. Riedel, L. Museur, et al.
Diamond polycrystalline films synthesized by chemical vapor deposition techniques present interesting feature for laser spectroscopy due to several advantages arising from their optical, electronic, thermal and mechanical properties. Their wide transmission band from the far IR to the UV make them attractive as optical devices for high-power laser beam. Moreover, with a wide band gap, a short carrier lifetime and a high damage threshold, diamond is an ideal semiconductor material for the fabrication of fast and solar blind VUV detectors. We report here results of laser studies performed with tow different objectives. With use of a pulsed VUV laser at 125 nm we have determined the photoconductive response of polycrystalline diamond detectors. With a CO2 laser we have investigated the polarization properties of auto-supported films having thicknesses smaller than the wavelength.
Laserspectroscopic study of defects in HTHP diamonds
Ilmo Sildos, Andris Osvet, Alexander P. Yelisseyev
Optical properties of HTHP diamonds can be changed by consecutive particle irradiation and temperature treatment which yields several nitrogen/nickel and vacancy related optical defects. Light-induced creation and destruction of the 546.8 nm defect has been shown to be possible. A new defect with well-pronounced vibronic spectrum was found with ZPL at 720 n,.
Impurity and stress distribution in diamond films investigated by laser-excited Raman and luminescence spectroscopy
S. Salvatori, M. C. Rossi, Fabrizio M. Galluzzi, et al.
Impurity and stress distribution in diamond films have been studied by microRaman and microphotoluminescence. Raman and PL lateral profiles reveal the existence of a large anisotropic stress at the grain boundary resulting in frequency splitting and linewidth variations of the TO phonon. The detection of an additional peak at 1326 cm-1 related to exagonal diamond phases and the high intensity reached by the 1.68 eV PL band at the coalescence region between two grains give evidence of preferential incorporation of defects at the grain boundary regions. Similarly, Raman and PL depth profiles indicate that the non-diamond intergrain tissue, abundant close to the substrate, induces compressive stress and represents a preferential site for Si diffusion.
Raman spectroscopy for 3D mapping of stress in CVD diamond
Igor I. Vlasov, Victor G. Ralchenko
Spatial distribution of intrinsic stress in chemical vapor deposition (CVD) diamond films was studied by confocal micro-Raman spectroscopy. For this purpose the series of high quality diamond films were grown by microwave plasma enhanced CVD. Both film-forming and isolated individual crystals from 20 to 200 micrometers lateral size and of different growth orientations were analyzed. Stress mapping was held on the continuous film surfaces and in a bulk of the isolated crystals. In surface analysis the Raman probing with 2 micrometers spatial resolution was able to detect smooth changes of stress only for large enough, 100-200 micrometers , grains. Thus most of the measurements have been done for the free-standing film of 600 micrometers thickness, where the grins with such sizes predominate. In bulk analysis the resolution of the Raman probing degenerates, but common tendencies of stress behavior have been traced. It was found that the majority of the high local stress regions observed are located in the vicinity of the grain boundaries. In many cases it is the grain boundary that separates domains of compressive and tensile stress. This can be explained by forming of incoherent interfaces in coalescent or twin crystallites during the growth process.
Processing
icon_mobile_dropdown
Precision shaping of a diamond surface by using interferometrically controlled laser-ablation method
Sandor Holly, Victor G. Ralchenko, Sergej M. Pimenov, et al.
A novel method for figuring and polishing diamond surfaces is described. It is a three step process, consisting of 1) a diffusion smoothing step using carbon reaction with certain materials at elevated temperatures, 2) a laser polishing and figuring step where UV laser ablation actively coupled with in situ interferometry provides the desired surface finish. The fist step of the process uses carbon diffusion into a hot iron surface to achieve an initial, relatively smooth surface of the as grown chemical vapor deposited (CVD) diamond surface. The technique can be used on any size CVD diamond and may be applied to curved surfaces. The second step, excimer laser ablation, is the backbone of the proposed method. By using an in situ, interferometric surface measuring and monitoring capability, diamond material may be removed from the surface in an accurately controlled manner, both in depth and width. The method is conceptually similar to single point diamond turning for figuring the optical surfaces of metal mirrors. The last step uses the properties of ion beam technology to change the top layer of the diamond surface into a soft and easily polishable amorphous carbon. The final surface finish of the accurately figured surface is obtained by conventional, high quality polishing techniques.
Processing of diamond by laser beam irradiation
Masanori Yoshikawa, Atsushi Hirata
YAG and ArF excimer laser beams, of which wavelengths are 1.06 micrometers and 193 nm respectively, have been applied to processing of a variety of diamonds. Cutting and smoothing of natural, CVD and sintered diamonds have been performed. CVD diamond films were prepared by arc discharge plasma jet CVD and microwave plasma CVD, and sintered diamonds contain metallic or ceramic binder have been used. Fundamental removal processes of diamond with YAG and ArF excimer laser have been investigated using natural single crystal and CVD diamonds in various atmospheres changing laser irradiation conditions such as average power, energy density and pulse repetition rates. Cutting of natural and CVD diamonds with YAG laser proceeds at higher peal power that occurs at lower pulse repetition rates. Smooth surfaces are obtained by excimer laser irradiation at the incident angle of 80 percent. In the cases of the processing with YAG laser, the effect of local heating by laser beam irradiation mainly assists the diamond processing, and diamond appears to be removed after graphitization and oxidization following vaporization in the atmosphere contains oxygen. The temperature measurement was carried out at backside of irradiation surface, and increase of temperature when YAG laser beam was irradiated was larger than that when excimer laser was irradiated. On the contrary, the detection of C, C2, C+, O2 and CO from the emission at the irradiation area with ArF excimer laser beam suggest that processing partly proceeds by the separation of carbon atoms from the surface of diamond after braking bonds between carbon atoms caused by laser beam. Cutting of sintered diamond with metallic binder was difficult because metallic binder remains in the groove while ceramic binder was easily removed. Processing technique using laser beams has been applied to surface planing, chip preparation and edge formation of CVD diamond and curved surface formation on sintered diamond. Surface planing was carried out by directing the YAG laser beam parallel to the surface of diamond films and diamond chips were prepared by the combination of cutting and surface planing techniques. A sharp edge was formed between the surfaces which cut by laser beam and mechanically polished. Round nose was formed by gradually rotating the sintered diamond following YAG laser beam irradiation.
CVD diamond TEM sample preparation by laser machining
James E. Butler, D. J. Vestyck Jr., A. Gilmore, et al.
The defect structure of diamond films grown by microwave plasma chemical vapor deposition (CVD) in studied by using laser machining to slice thin sections from free standing films ca. 200 microns thick. This technique has enabled the examination of the defects at the nucleation and growth surface of optically clear CVD diamond films. A cw Q- switched Nd3+/YAG laser was used to slice 1 to 15 micron thick wedges, ca. 3mm in length from 150 to 220 micron thick diamond films. The edges of the as cut wedges were thin enough for examination by transmission electron microscopy. Subsequent ion milling was used to thin the edges further. Remarkably low defect densities are observed at the growth surface after 150 microns of growth.
Structure and electronic properties of laser-ablated diamond film surface
Sergej M. Pimenov, E. D. Obraztsova, A. V. Karabutov, et al.
The effects of laser-induced structural modifications of the diamond surface are considered in relation to i) laser activation of diamond for direct electroless metallization ii) enhanced electron field emission from laser-ablated diamond films. It is shown that both the catalytic activity for electroless metal plating and reduced emission fields of the laser-ablated diamond surface correlate with the modifications in the valence-band structure, a specific feature of which is the appearance of the occupied electronic states in the gap. The laser ablation technique is applied for fabricating periodical microstructures at the diamond film surface, and results of the field emission testing of the produced 1D microstructures are presented.
Enhanced field emission characteristics from nanocrystalline diamond films through UV laser post-growth modification
M. V. Ugarov, V. P. Ageev, A. V. Karabutov, et al.
A significant reduction of electron field emission thresholds resulting from ArF laser irradiation of nanocrystalline diamond films in borazine and ammonia atmospheres is reported for the first time. The change of emission characteristics is not connected with either laser surface graphitization or formation of bulk defects. XPS surface analysis and Raman spectroscopy data form these samples shows that laser irradiation results in the synthesis of ultra thin layers of boron-carbon-nitrogen and in B and N atoms intergrain penetration into the film to a depth above 100 angstrom. The synthesis of the B-C-N ternary and existence of sp2 bonded C-N compounds is demonstrated.
Laser-assisted etching of diamonds in air and in liquid media
George A. Shafeev
Etching with the help of a copper vapor laser of diamond polycrystalline CVD films is studied in various surrounding media. Diamond samples are virtually transparent at this wavelength, and the coupling of laser radiation to diamond is due to the formation of a thin graphitized layer at the diamond surface. The etching rate in liquid media is slightly higher than in air at otherwise equal conditions and is as high as 50 micrometers /s under the etching with a scanning laser beam. The diamond surface etched in liquids is virtually free of the glassy carbon layer. Electroless deposition of metals on the laser-etched features is studied to compare the catalytic activity of he diamond surface etched in air with that etched in liquids. Possible mechanisms are discussed responsible for the observed difference both in the structure of the etched area and in the electroless metal deposition onto the surface etched in various media.
Concentrated solid solutions and dissolution of diamond and cubic boron nitride
M. S. Saidov, Mukhsin Kh. Ashurov
The solubility in the multicomponent system is discussed. Considering the molecular elements and some combinations of elements not shown on the traditional phase diagrams as the new chemical compounds the conditions of the formation of their continuous solid solutions (CSS) with the single covalent bond are suggested. Using the valences and covalent radii of B, C, N, Be, O, Al, and P and possibility of the formation of CS, based on diamond and cubic boron nitride is substantiated. To back up such a possibility the brief review of the experimental data on the (IV2)x(III- V)1-x and (IV2)x(II-VI)1-x CSS are presented. Taking into account the advantages of thinning of chemical vapor deposited (CVD) diamond plates with a molten alloys and the idea on substitutional and interstitial liquid solutions for the processing of the polycrystalline CVD diamond plates by the effective dissolution a number of molten alloys are predicted.
Optical properties of laser-modified diamond surface
A. V. Khomich, V. V. Kononenko, Sergej M. Pimenov, et al.
The results of laser polishing of 350 micrometers thick free- standing diamond films are reported. The polishing was performed with a grazing beam of a copper vapor laser. It is shown that the laser polishing conditions and the resulting surface roughness are controlled by varying an angle of incidence of a scanning laser beam during polishing. The surface roughness of the as-grown films was reduced by an order of magnitude and a minimum roughness of Ra equals 0.38 micrometers was achieved as a result of the two-step polishing. Optical transmission in the UV-visible spectral range of the diamond films polished under the optimized conditions was found to be close to the optical transmission of the mechanically polished diamond film. Properties of the laser-graphitized layer at the diamond surface were studied with optical spectroscopy techniques in the process of oxidative removal of the layer with increasing temperature of the oxidation in ambient air. The optical properties and oxidation stability of the laser-modified surface layer were found to change throughout its thickness from the surface to the diamond interface, depending on the laser polishing regime.
Oxygen-assisted laser cutting and drilling of CVD diamond
V. V. Migulin, Victor G. Ralchenko, Y.-J. Baik
A Nd:YAG laser was used for cutting and drilling of thick free-standing diamond films produced by microwave plasma chemical vapor deposition. The laser machining rate was evaluated at different irradiation parameters such as laser power, beam scanning velocity and number of repetitive scans. Carbon oxidation in presence of oxygen flow in the cutting/drilling area is shown to result in smooth and clean sidewalls and top surface around grooves and holes. A beneficial effect of O2 stream on cutting and drilling rate was also observed.
Applications
icon_mobile_dropdown
Diamond photodetectors for UV laser-based applications
Robert D. McKeag, Richard B. Jackman
Many laser-based applications require a robust and sensitive deep UV photodetector, properties not offered by existing solid state devices which are based on silicon. Thin film CVD diamond offers a solution to this problem, but careful device design and passivation of defects within the diamond are required before this material can be used to fabricate high performance devices. This paper reviews the optoelectronic properties of diamond films, considers how they may be modified and surveys the current state-of-the- art in diamond photodetector technology.
CVD diamond wires and tips for x-ray detection: growth and characterization by SEM and micro-Raman spectroscopy
Claudio Manfredotti, F. Fizzotti, A. Lo Giudice, et al.
We present a systematic study of the growth of polycrystalline diamond thin films on W wires and tips by hot filament assisted chemical vapor deposition for x-ray detection purposes. We carry out correlations between scanning electron microscopy (SEM) observations and micro- Raman spectra, while varying different growth parameters. SEM observations show a uniform covering of the substrate, with growth rates ranging from 0.5 to 1.5 micrometers /h. All (mu) - R spectra show a well defined diamond peak at 1330.8-1333.7 cm-1 together with abroad structure at 1400-1600 cm-1 and a luminescence background extending over the whole scanned range. A close analysis shows that best quality is obtained with the lowest diameter substrates, at the lowest CH4 concentration and at a low pressure. Some depositions have been studied as x-ray detectors and their sensitivity at low energy and 6 MeV beam evaluated, showing a good response with respect to standard ionization chambers.
Optical characterization of graphitized layers in ion-implanted diamond
R. A. Khmelnitskiy, V. A. Dravin, S. D. Tkachenko, et al.
Optical interference studies of graphitized layers formed in diamond by ion bombardment and annealing provided the data on the depth and the thickness of the layers as well as their optical parameters. The latter were found to be close to those of dispersed graphite. Cathodoluminescence analysis of diamond samples implanted with fluences below and above the threshold of formation of the graphitized layer has shown that the conditions of formation and/or properties of the optical centers in the area with the buried graphite layer are different form those in the area without the layer which might to be due to the considerable tension in the part of the crystal between the surface and the buried graphitized layer.
Thermal Properties
icon_mobile_dropdown
Spatial distribution of thermal conductivity of diamond wafers as measured by laser flash technique
Victor G. Ralchenko, A. Vlasov, Igor I. Vlasov, et al.
Thermal conductivity perpendicularly to diamond film surface was measured using a laser flash technique. Polycrystalline diamond wafers of up to 500 microns thickness and 2.25 inch diameter were produced in microwave plasma at different deposition conditions. Thermal conductivity (TC) was determined from heat propagation time across the wafer after short pulse of a Nd:YAG laser absorbed at sample surface. Distributions of TC along wafer radius were measured with 1 mm spatial resolution, they correlate to optical absorption, Raman diamond peak width and amorphous carbon concentration in the material. The best TC values of 18 W/cmK were measured for selected samples.
Generation of acoustic phonons in diamond by laser excitation of the buried implanted layer
T. I. Galkina, A. Yu. Klokov, R. A. Khmelnitskiy, et al.
A specific version of the hat pulse technique as applied to diamond is presented. The conventional heat pulse technique implies generation of acoustic phonons near the surface of a solid and analysis of their propagation in the crystal utilizing a certain phonon-sensitive detector. Generation of phonons is usually achieved with the help of a pulsed laser whose quanta are absorbed at or near the surface either by a metal film deposited onto a sample or by the sample itself. In the case of diamond, the latter version requires a powerful UV source and special optics that present some difficulties.
Laser measurements of optical and thermal properties of CVD diamond at high temperatures
Vitali I. Konov, Serge V. Garnov, O. G. Tsarkova, et al.
The laser express technique has been applied to high temperature measurements of CVD diamond reflectivity R and absorption coefficient (alpha) for radiation with 1.06 mm wavelength as well as heat capacity. It was found that at T > 1000 degrees C and heating cycles of a few seconds the sample surface layer with thickness of 100 nm becomes graphitized that leads to dramatic growth of (alpha) from initial value of about 10 cm-1. The obtained results on heat capacity at T >= 800 degrees C are well matched with the known data at lower temperatures.
Mechanisms of phonon scattering in microcrystalline diamond films
V. B. Efimov, L. P. Mezhov-Deglin
The investigation of the thermal conductivity of diamond films gives us a very important information about mechanisms of heat transport and scattering processes in bulk. 1 . Iffrom the specific heat one can obtain characteristics of interaction between atoms and molecules, the study of the transport characteristics (electric and thermal conductivity, thermopower and so on) gives the information about scattering processes in phonon and electronic systems and scatterings on defect structures in solids. 2. The knowledge of absolute values of the thermal conductivity is the necessary for practical application of diamond films as a high heat transmission substrate. 3 . Diamond is a very convenient model system with very high Debye temperature (E 22OO K) for studies the phonon scattering processes in a wide temperature range. The room temperature is low temperature for diamond in comparison with any another materials. The phonon wave length is of the order of ten lattice parameter d3O A at room temperature and ofthe order 500 d '- 1500 A at helium temperatures.