|
|
|
The deposition of high quality diamond films at high linear growth rates and substrate temperatures for microwave-plasma chemical vapor deposition is disclosed. The linear growth rate achieved for this ...
Deposition Of Cubic BN On Diamond Interlayers
Thin films of polycrystalline, pure, cubic boron nitride (c-BN) formed on various substrates, according to proposal, by chemical vapor deposition onto interlayers of polycrystalline diamond. Substrate ...
1990-11-01
We have used x-ray diffraction to characterize diamond films grown in three characteristic morphologies by chemical vapor deposition. Each morphology has a fiber texture about the growth direction; we report the crystal axis aligned in this direction for each morphology. In all cases the average lattice constant agrees with that of bulk diamond; we report the range of strain in each sample.
Synthesis and characterization of fine grain diamond films
A fine grain diamond film has been developed by microwave plasma assisted chemical vapor deposition. Various analytical techniques, including Rutherford backscattering, proton recoil analysis, Raman spectroscopy, and X-ray ...
Diamond Ablators for Inertial Confinement Fusion
2005-06-21
Diamond has a unique combination of physical properties for the inertial confinement fusion ablator application, such as appropriate optical properties, high atomic density, high yield strength, and high thermal conductivity. Here, we present a feasible concept to fabricate diamond ablator shells. The fabrication of diamond capsules is a multi-step process, which involves diamond chemical vapor deposition on silicon mandrels followed by polishing, microfabrication of holes, and removing of the silicon mandrel by an etch process. We also discuss the pros and cons of coarse-grained optical quality and nanocrystalline chemical vapor deposition diamond films for the ablator application.
High temperature UV/Vis spectroscopy of diamond
1995-04-01
The high temperature UV/VIS absorption of diamond is being investigated as part of the research on the homoepitaxial growth of thin diamond films by chemical vapor deposition (CVD). The absorption characteristics at temperatures typical of diamond CVD reactors are important for the examination of the effect of in situ excimer laser irradiation on the nucleation, growth and morphology of diamond films.
1992-08-31
Schottky diodes were fabricated using sputter deposited silver contacts to boron doped polycrystalline diamond thin films grown by a hot-filament chemical vapor deposition process with trimethyl borate as an {ital in} {ital situ} dopant source. High forward current density and a high forward-to-reverse current ratio were exhibited by these diodes. Current density-voltage and capacitance-voltage-frequency characteristics of these diodes are very similar to those of Schottky diodes fabricated using a single-crystal diamond substrate.
2006-01-01
According to roles of atomic hydrogen, methyl and acetylene in diamond film chemical vapor deposition (CVD) in CH and CHO systems, two micro parameters and their criteria were established, viz., methyl mole fraction [CH3] and ratio of atomic hydrogen mole fraction to acetylene [H]/[C2H2], corresponding to the growth of diamond and etching of non-diamond carbon, respectively. By simulating gas-phase chemistry in CHN environment, equilibrium compositions for various nitrogenous mixtures were obtained. A CHN ternary phase diagram for diamond chemical vapor deposition under low pressure was constructed and influence of activation temperature on diamond domain was calculated. They were proved basically logical by over eighty experimental points in literatures, confirming th...
Tribological properties of diamond films grown by plasma-enhanced chemical vapor deposition
1989-01-01
Uniform and continuous diamond films have been deposited on Si, Mo, and many other substrates by plasma-enhanced chemical vapor deposition. We have developed processes to enhance the adhesion of diamond films to metal substrates for tribological applications. The tribological properties of the diamond films are found to be significantly different depending on their morphology, grain size, and roughness. However, under all cases tested using a ring-on-block tribotester, it is found that for diamond films with a small grain size of 1--3 mum, the coefficient of friction of the diamond films sliding against a steel ring under lubrication of a jet of mineral oil is about 0.04
In situ surface roughness measurement during PECVD diamond film growth
To investigate the development of surface morphology and bulk optical attenuation in diamond films, we have followed diamond film growth on silicon by in-situ laser reflection interferometry in a microwave plasma chemical vapor deposition system. A model for the interpretation of the reflectivity data in terms of film thickness, rms surface roughness and bulk losses due to scattering and absorption is presented. Results are compared with ex situ measurements of these quantities and found to be in good agreement.
In situ surface roughness measurement during PECVD diamond film growth
1995-06-01
To investigate the development of surface morphology and bulk optical attenuation in diamond films, we have followed diamond film growth on silicon by in-situ laser reflection interferometry in a microwave plasma chemical vapor deposition system. A model for the interpretation of the reflectivity data in terms of film thickness, rms surface roughness and bulk losses due to scattering and absorption is presented. Results are compared with ex situ measurements of these quantities and found to be in good agreement.
Metalorganic Chemical Vapor Deposition of Ruthenium-Doped Diamond like Carbon Films
We investigated metalorganic precursor deposition using a Microwave Electron Cyclotron Resonance (ECR) plasma for depositing metal-doped diamondlike carbon films. Specifically, the deposition of ruthenium doped ...
Epitaxial growth of B-doped high quality diamond film on cBN surface by chemical vapor deposition
1995-12-31
B-doped high quality diamond epitaxial films have been obtained on high-pressure synthesized cBN crystals by dc glow discharge chemical vapor deposition (CVD). The deposition conditions and the orientation of cBN crystal are important to diamond oriented nucleation and epitaxial growth. The micro-Raman spectroscopy measurement indicates that the quality of the diamond film grown on cBN (100) surface is close to that of natural diamond. The scanning electron microscopy (SEM) observation shows that the epitaxial film has very smooth surface. The specific resistance of the B-doped epitaxial film is about 0.1 ohm{center_dot}cm.
1995-08-01
Diamonds have been deposited rapidly under low pressures (< 0.1 Torr) via hot filament chemical vapor deposition (HFCVD) on either scratched or mirror-smooth single crystalline silicon and titanium with nucleation densities of 10{sup 9}-10{sup 11}/cm{sup 2}. The nucleation density increases with the pressure decreases. Hydrogen and methane were used as the gaseous source. Raman spectroscopy and scanning electron microscopy (SEM) were used to analyze the obtained films. These results breaks through the limit that diamond film can only be synthesized above 10 Torr, showing a promising prospect that, as is essential for heteroepitaxial growth of monocrystalline diamond films, diamond films can be easily nucleated on unscratched substrate via Hot Filament CVD.
2005-01-01
The usual weekly laboratory experiment for the upper-division modern physics lab was replaced with a theme of studying diamond films grown on natural diamond. The diamonds were grown at University of Alabama at Birmingham and were studied at university physics laboratories at UAB, Alabama A and M University, University of the South, and University of North Texas. Undergraduate students measured the molar fraction of 13C in diamond films grown by a microwave-assisted chemical vapor deposition process on oriented diamond plates. The molar fraction of 13C for all diamond films except the 100% and 1% was determined from Rutherford backscattering measurements at 150o. Raman scattering of a 514.5 nm Ar-ion laser beam from the same diamond films provided empirical determination of the molar fraction of 13C of the diamond ...
Synthesis and morphology of CVD diamond on Ta and TaC film
1993-03-01
Synthetic diamond films have been deposited on the Si(111) surface, polycrystalline Ta plate, TaC/Si, and TaC/Ta substrates using an electron assisted chemical vapor deposition (EACVD) method. The effects of substrate pretreatment and existence of carbide layer on the diamond nucleation, subsequent growth and morphology have been studied. The substrate pretreatment, scratching by diamond powder, affects nucleation behavior, subsequent growth and morphology of diamond. Existence of carbide layer and formation of carbide on the substrate affects nucleation density, growth rate and morphology of diamond. (orig.)
Boron doped polycrystalline diamond films for strain sensing applications
1995-12-31
It has been recently established in our work and others that boron-doped polycrystalline diamond films (PDF) have piezoresistivity (PZR). This property opens PDF to the field of sensor applications using strain sensing. Polycrystalline diamond films have been prepared with microwave plasma enhanced chemical vapor deposition (CVD) method and boron-doped to p-type semiconductors. In addition, by combining the piezoresistive effect in doped PDF and the insulating property of undoped PDF, whereby doped diamond resistors reside on a dielectric diamond substrate diaphragm, a monolithic all-diamond microstructure for examining the strain response of patterned p-doped diamond PZRs was fabricated and characterized. This work examines some critical issues of diamond for strain sensing applications such as its rupture stress and edge stress of diamond diaphragm and the high temperature responses of a diamond strain sensor.
2009-01-01
A tungsten-carbide gradient coating (WCGC) was prepared by reactive sputtering as an intermediate layer on the cemented carbide, WC-13wt.% Co, substrate to improve the nucleation, smoothness and adhesion of diamond film. The diamond film was deposited by hot filament chemical vapor deposition (HFCVD). The effects of the substrate temperature on the WCGC and the diamond film were investigated. The characterization of the WCGC and the diamond films was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), micro-Raman spectroscopy and Rockwell hardness indentation. It is found that the WCGC plays an important role in improving the nucleation, smoothness and adhesion of diamond film; and the diamond films exhibit better quality and adhesion as ...
2009-01-01
In this work, we study the influence of oxygen additive in the gas phase on hydrogen impurity incorporation into thick nanocrystalline diamond (NCD) films. Various diamond samples were grown on large silicon wafers of 5.08 cm diameter by adjusting the amount of oxygen and nitrogen additives into a conventional CH4/H2 plasma while keeping the other parameters constant using a 5-kW microwave plasma-assisted chemical vapor deposition (MPCVD) reactor. The morphology, crystalline quality, and hydrogen impurity content of the produced diamond samples were characterized using scanning electron microscopy, micro-Raman spectroscopy, and Fourier transform infrared (FTIR) spectroscopy, respectively. The Raman and the FTIR spectra of the diamond samples indicate that on increasing the amount of oxygen...
1990-01-01
High quality diamond films have been rapidly synthesised by the DC arc discharge plasma CVD in a hydrogen-methane mixture gas. The properties of the films are tested and analyzed by scanning electron microscopy, X-ray diffraction and Raman spectra. In order to find out the growth mechanism of vapor deposited diamond, in situ optical emission spectra of plasma under practical growth conditions are measured. It is found that the key factor of rapid growth diamond film is the presence of a large number of atomic hydrogen in the plasma
Characterization of crystalline diamond incorporated diamond-like carbon films
2010-01-01
The purpose of this paper is to show the production and characterization of diamond-like carbon (DLC) films with incorporated crystalline diamond (CD), produced by plasma enhanced chemical vapor deposition. CD-DLC films were characterized by scanning electron microscopy, X-ray diffraction, atomic force microscopy and Raman scattering spectroscopy. Wetting contact angle, stress and friction coefficient were also evaluated. Our results demonstrated CD-DLC films are more hydrogenated and hydrophobic, with higher fiction coefficient. The stress values kept almost constantly.
This paper reports on the surface topography of diamond thin films deposited on silicon charted by scanning tunneling microscopy (STM). This study addresses the initial nucleation of diamond growth on Si, and the faceted structure of the diamond films. The results were obtained from an in-air STM system with tunneling currents between 0.2 and 3 nA. For studies of the diamond nucleation, samples were prepared by timed growth up to 60 min in a microwave plasma chemical vapor deposition (CVD) system. Diamond films with thicknesses in the 1-2 {mu}m range were prepared by hot-filament CVD and examined by STM to determine the morphology of the diamond growth surface. The presence of diamond was verified by Raman spectroscopy. The STM images show that the surface is uniformly affected in the first 30 min of growth and diamond nuclei are identified after 60 min of growth. The thick films showed topography with facets on the surface similar to those seen from scanning electron microscopy results. The surface of these facets have been examined as well as the area between the facets. Elongated ridge structures are observed between different facets on the surface.
Amorphous hard boron nitride films prepared by plasma enhanced chemical vapor deposition
1995-12-31
Amorphous boron nitride films were prepared on Si substrates by plasma enhanced chemical vapor deposition with a BCl{sub 3}-N{sub 2}-Ar-H{sub 2} gas mixture. The surface of the resulting films indicated a Knoop hardness of 60000-80000 N/mm{sup 2} at a loading force of 100 mN. Scratching test revealed that the critical load of the boron nitride films was higher than that of diamond like carbon films prepared on Si substrates.
Thin diamond films for tribological applications
1989-01-01
Diamond films have been deposited on Si, Mo and many other substrates by microwave and radio frequency plasma enhanced chemical vapor deposition. Although the adhesion between the diamond film and most of the metal substrates is poor due to residual thermal stress from the mismatch of thermal expansion coefficients, the authors have developed processes to promote the growth of uniform and continuous diamond films with enhanced adhesion to metal substrates for tribological applications. The tribological properties of these films are measured using a ring-on-block tribotester. The coefficients of friction of diamond films sliding against a 52100 steel ring under the same experimental conditions are found to be significantly different depending on the morphology, grain size and roughness of the diamond films. However, under all cases tested, it is found that for uniform ...
Ion-beam polishing of diamond thin films
1995-12-31
Planarization of diamond thin films has been carried out using a remote electron cyclotron resonance (ECR) oxygen plasma under a negative bias. Diamond thin films were synthesized by hot filament chemical vapor deposition (HFCVD). The surface roughness (R{sub a}) of the diamond films could be considerably reduced from 0.2 {micro}m to 0.05 {micro}m using the ECR oxygen plasma. Low planarization and a high etching rate of diamond films were observed for an incident angle of the ion beam to the film surface normal below 45 degrees. High applied bias above {minus}600 V caused secondary discharge effects, resulting in inhomogeneous etching. With an increase in incident angle, needle-like morphology was observed in the diamond film.
Diamond nucleation and growth on titanium silicon carbide (Ti3SiC2) slices were investigated by microwave plasma-enhanced chemical vapor deposition (MPECVD) in a hydrogen and methane gas mixture for the first time. For comparison, diamond deposition on Si wafers under the same conditions was also investigated. A much higher diamond nucleation density and a much higher film growth rate were obtained on Ti3SiC2 compared with on Si. The deposition time for the formation of fully dense diamond film was much shorter on Ti3SiC2 than on Si. Furthermore, the diamond films on Ti3SiC2 show smoother surface with a preferred [0 0 1] orientation and exhibit better adhesion than those on Si. These results indicate that Ti3SiC2 has great potentials to be used as both substrate materials and interlayers on metals for diamond thin film deposition and application. It may greatly expand the tribological applications of both Ti3SiC2 and diamond thin films.
Effects of implant copper layer on diamond film deposition on cemented carbides
2001-01-01
The deposition of high-quality diamond films and their adhesion on cemented carbides are strongly influenced by the catalytic effect of cobalt under typical deposition conditions. Decreasing Co content on the surface of the cemented carbide is often used for the diamond film deposition. But the leaching of Co from the WC-Co substrate leading to a mechanical weak surface often causes a poor adhesion. The authors adopted an implant copper layer prepared by vaporization to improve the mechanical properties of the Co-leached substrate. The diamond films were grown by microwave plasma chemical vapor deposition from CH4:H2 gas mixture. The cross section and the morphology of the diamond film were characterized by scanning electron microscopy (SEM). The non-diamond content in the film was analyzed by Raman spectroscopy. The effects of pretreatment on ...
2010-01-01
In this work, two approaches were developed to extend the coating area of diamond by continuous deposition in a plasma-assisted chemical vapor deposition (CVD) method above the liquid. The techniques were based on the methods previously developed by our research group and the characteristic was to use dc (direct current) plasma generated between the liquid surface and the metal electrode. In the first approach, a tungsten rod was rotated in a chamber at reduced pressure so that a diamond film was formed as a 'belt' in 6mm width around the side of the rod. The deposited diamond was polycrystalline with a grain size of 1-3mm. The film thickness increased almost linearly with deposition time, whereas the grain size was almost constant against the deposition time. The second approach was for a...
Hydrogen in nano-diamond films: experimental and computational studies
2008-01-01
We present studies related to the incorporation of hydrogen and its bonding configuration in diamond films composed of diamond grains of varying size which were deposited by three different methods: hot filament (HF), micro wave (MW) and direct current glow discharge (dc GD) chemical vapor deposition. The size of the diamond grains which constitute the films varies in the following way: hundreds of nm in the case of HF CVD ("sub-micron size", 300 nm), tens of nm in the case of MW CVD (3-30 nm) and a few nm in the case of dc GD CVD ("ultra nano-crystalline diamond", 5 nm). Secondary ion mass spectroscopy (SIMS) and high resolution electron energy loss spectroscopy (HR-EELS) were applied to investigate the hydrogen trapping in the films. The hydrogen retention of the diamond films increases ...
Field emission from bias-grown diamond thin films in a microwave plasma
A method of producing diamond or diamond like films in which a negative bias is established on a substrate with an electrically conductive surface in a microwave plasma chemical vapor deposition system. The atmosphere that is subjected to microwave energy includes a source of carbon, nitrogen and hydrogen. The negative bias is maintained on the substrate through both the nucleation and growth phase of the film until the film is continuous. Biases between -100V and -200 are preferred. Carbon sources may be one or more of CH.sub.4, C.sub.2 H.sub.2 other hydrocarbons and fullerenes.
Field emission from bias-grown diamond thin films in a microwave plasma
A method of producing diamond or diamond like films in which a negative bias is established on a substrate with an electrically conductive surface in a microwave plasma chemical vapor deposition system. The atmosphere that is subjected to microwave energy includes a source of carbon, nitrogen and hydrogen. The negative bias is maintained on the substrate through both the nucleation and growth phase of the film until the film is continuous. Biases between -100V and -200 are preferred. Carbon sources may be one or more of CH.sub.4, C.sub.2 H.sub.2 other hydrocarbons and fullerenes.
Field emission from bias-grown diamond thin films in a microwave plasma
A method of producing diamond or diamond like films in which a negative bias is established on a substrate with an electrically conductive surface in a microwave plasma chemical vapor deposition system. The atmosphere that is subjected to microwave energy includes a source of carbon, nitrogen and hydrogen. The negative bias is maintained on the substrate through both the nucleation and growth phase of the film until the film is continuous. Biases between -100V and -200 are preferred. Carbon sources may be one or more of CH.sub.4, C.sub.2 H.sub.2 other hydrocarbons and fullerenes.
Potential of diamond films for electronic device application; Diamond no denshi zairyo eno oyo
1998-09-20
The results of recent researches on diamond thin films aiming at their practical application are discussed. Efforts have been under way for the synthesis of diamond thin films using an end-launch type microwave plasma CVD (chemical vapor deposition) unit provided with a stainless steel reactor vessel 6 inches in diameter and supposedly capable of inhibiting the incorporation of impurities from the reactor vessel. Now, for the first time in the world, undoped CVD diamond, with its physical properties superior to the best physical properties of natural diamond, is synthesized out of a process accomplished under unprecedented deposition conditions. Furthermore, an endeavor has been under way for the synthesis of boron-doped p-type diamond thin films using trimethylboron as doping gas. As the result, a success is won in the impurity doping process, and a p-type diamond film is synthesized, equipped with hole mobility that is the highest for a CVD synthesized diamond thin film. It is deemed that the artificial synthesis of diamond thin films has at last arrived at a level where the product can be superior to natural diamond. 14 refs., 7 figs., 2 tabs.
Homogeneous and large-area diamond film formed using multi-filament chemical vapor deposition
1994-08-15
Diamond synthesis under metastable conditions by chemical vapor deposition (CVD) has been a subject of considerable interest in the past decade. Hot-filament chemical vapor deposition (HFCVD) has been extensively used to deposit diamond films. The advantages of this method are its simplicity, reproducibility, and potential for large-area applications. Coiled filaments, such as tungsten, tantalum, and rhenium wires, have been generally used in the HFCVD method. However, the distortion of these filaments makes it difficult in practice to secure homogeneous and large-area diamond films. To cope with filament deformation and obtain homogeneous deposition of diamond film over large areas, researchers have used straight wires to replace coiled wires as filaments. Growing diamond films of uniform thickness and high quality over large areas and at suitable growth rates also requires enhanced substrate temperature uniformity. A further issue is that contamination of diamond films by metallic impurities originating from the filament has been reported in some studies, but not in others. In the research reported here, the authors attempted to synthesize homogeneous, high-quality diamond film with a large area (70 mm x 70 mm) using a nine-filament diamond CVD process. The authors also examined the metallic impurities in diamond film grown using this method.
Effect of grain boundary on local surface conductivity of diamond film
2009-01-01
In this article, the direct experimental evidences to determine the effect of grain boundary on local surface conductivity (SC) of diamond films were provided by the measurement using double probe scanning electron microscopy (SEM) technology. Undoped diamond films with (001) orientation were first grown by microwave plasma enhanced chemical vapor deposition and were then hydrogenated at different conditions for SC measurement. In the SEM system, double probes with tiny tip radius severed as two leads were moved along and contacted with the diamond film surface to directly test the local SC of diamond film. The surface electrical property results indicate that for the same distance between the two probes, the local SC of the area across grain boundary is much higher than that of area without grain boundary for the same duration of hydrogenation degrees. In addition, local SC ...
A cathodoluminescence study of boron doped {111}-homoepitaxial diamond films
2010-01-01
In this work we use cathodoluminescence (CL) at liquid helium temperature to investigate the boron incorporation in {111}-homoepitaxial diamond films, grown outside the visible plasma ball by the Microwave plasma-assisted chemical vapor deposition (MPCVD) technique. The boron concentration of this set of films covers the whole possible doping range divided into four parts: Low doping (5x10^1^62x10^2^1cm^-^3). The phase separation occurs for very high boron concentrations, between the diamond phase (sp^3 carbon) and the other components of the layer, namely sp^2 carbon and boron. A part of them is accumulated outside the diamond lattice. This detailed cathodoluminescence investigation of {111}-homoepitaxial diamond films has led to determining the doping range of the films and following the...
Evaluation of abrasion resistance and adhesion strength of brazed diamond film by a shearing test
1991-08-01
A shear tool tip comprising a thick polycrystalline diamond film brazed to the tool substrate was made and subjected to a shearing test in order to check the feasibility of using diamond coatings made by chemical vapor deposition on shearing tools. The material to be sheared by this diamond tool was a reel of polishing tape coated with very hard SiC particles which cause severe wear on the shearing tool. The shearing experiment was continued until the tool was worn away to a point where it could no longer sever the work material. The tool life was tested against that of two other materials for the purposes of comparison. The results showed that the life of the shearing tool with brazed on diamond film was 100 times longer than that of a tungsten carbide alloy tool and four times longer than that of a sintered diamond tool. (orig.).
Microstructural effects on the hardness, elastic modulus and fracture toughness of CVD diamond
1998-12-31
The hardness, elastic modulus, and fracture toughness of chemical vapor deposited (CVD) polycrystalline diamond have been investigated on several thick ({approximately}100 {micro}m) free-standing films with regard to the grain size, impurity content and failure mechanisms. Micro-hardness measurements using Vickers indentation, in conjunction with Young`s modulus measurement techniques such as nano-indentation, were employed to estimate the indentation fracture toughness. The toughness of CVD diamond was increased through the addition of non-diamond carbon, which promoted intergranular fracture and enhanced the toughness by grain bridging.
Plasma-enhanced deposition of nano-structured carbon films
2005-01-01
By pre-treating substrate with different methods and patterning the catalyst, selective and patterned growth of diamond and graphitic nano-structured carbon films have been realized through DC Plasma-Enhanced Hot Filament Chemical Vapor Deposition (PE-HFCVD). Through two-step processing in an HFCVD reactor, novel nano-structured composite diamond films containing a nanocrystalline diamond layer on the top of a nanocone diamond layer have been synthesized. Well-aligned carbon nanotubes, diamond and graphitic carbon nanocones with controllable alignment orientations have been synthesized by using PE-HFCVD. The orientation of the nanostructures can be controlled by adjusting the working pressure. In a Microwave Plasma Enhanced Chemical Vapor Deposition (MW-PECVD) reactor, high-quality diamond films have been synthesized at low temperatures (310 degree ...
Dose rate effects on the performance of MWCVD diamond films as TL gamma radiation dosimeter
2010-01-01
Dose rate effects on the thermoluminescence (TL) properties of undoped and 750 ppm nitrogen doped microwave chemical vapor deposition (MWCVD) diamond films were analyzed. The diamond samples were exposed to 2.4-20.67 Gy/min dose rates from a 60Co source. The TL glow curve of undoped sample showed no apparent dose rate effects. The doped diamond film exhibited dose rate effects consisting in a 10-30% integrated TL increase as the dose rate increased. The TL response as a function of dose rates showed a nonlinear behavior for the doped sample contrary to the undoped diamond film. The dose rate effects were evaluated through the determination of the kinetics parameters by fitting of the TL glow curves. The results indicate that chemical vapor deposition (CVD) diamond may present some dose rat...
1990-02-01
Both doped and undoped homoepitaxial diamond films were fabricated using microwave plasma-enhanced chemical vapor deposition (CVD). The conductivity of the diamond film is strongly affected by the surface treatment. In particular, exposure of film surface to a hydrogen plasma results in the formation of a conductive layer which can be used to obtain linear (ohmic) {ital I-V} characteristics of the Au/diamond contacts, regardless of the doping level. The proper chemical cleaning of the boron-doped homoepitaxial diamond surface allows the fabrication of Au-gate Schottky diodes with excellent rectifying characteristics at temperatures of at least 400{degrees}C.
Deposition of crackless freestanding diamond films on Mo substrates with Zr interlayer
2010-01-01
The Mo substrate with Zr interlayer, namely composite substrate, was employed to solve the problem of crack formation in the freestanding diamond film deposition. Freestanding diamond films deposited on the composite substrates by the direct current arc plasma jet chemical vapor deposition (CVD) method were investigated with scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and Raman spectroscopy. In addition, the stress distribution during the large area freestanding diamond film deposition on the composite substrate was analyzed based on the finite element model ANSYS. The results reveal that Zr interlayer can be easily destroyed during the post-deposition cooling process, which is helpful for stress release and crack avoiding in diamond...
1999-07-21
We have fabricated diamond anvils specially designed for use in ultra-high pressure electrical transport experiments. These anvils, which we refer to as ''designer anvils'', feature thin-film metal microprobes which are encased in a layer of high-quality, epitaxial, chemically vapor deposited (CVD) diamond. The synthetic diamond film ensures that the microprobes are survivable to Mbar pressures, and also serves to electrically insulate the microprobes from the high-pressure gasket. High-pressure resistivity experiments were performed on KI and FeO to pressures of approximately 1.8 and 1.7 Mbars, respectively. Future possible applications of designer anvils are also discussed. [electrical conductivity, synthetic diamond, band overlap, metallization, designer anvils]
2010-01-01
The micro-crystalline diamond (MCD) and fine-grained diamond (FGD) films are deposited on commercial silicon nitride inserts by the hot-filament chemical vapor deposition (HFCVD) method. The friction and cutting properties of as-deposited MCD and FGD films coated silicon nitride (Si3N4) inserts are comparatively investigated in this study. The scanning electron microscopy (SEM) and Raman spectroscopy are adopted to study the characterization of the deposited diamond films. The friction tests are conducted on a ball-on-plate type reciprocating friction tester in ambient air using Co-cemented tungsten carbide (WC-Co), Si3N4 and ball-bearing steel (BBS) balls as the mating materials of the diamond films. For sliding against WC-Co, Si3N4 and BBS, the FGD film presents lower friction coefficien...
A comparative study of p-type diamond films using Raman and transport measurements
2005-04-08
The influence of deposition temperature in the properties of synthetic diamond films grown by two different chemical vapor deposition (CVD) techniques, hot-filament- and microwave-plasma-assisted, was investigated. These samples were obtained using the optimal growth conditions previously achieved in this work. Raman spectroscopy was employed in order to investigate the diamond film quality as a function of the deposition temperature. It was found that the nondiamond carbon bands decrease as the deposition temperature increases for both the deposition methods, leading to higher-quality diamond films. The micro- and macro-Raman spectra showed that the nondiamond band is already present in a single diamond grain. Both techniques provided well homogeneous diamond films and with equivalently good quality. Boron-doped diamond films with different carrier concentration levels were also studied. In order to get details about the electrical properties of the films, resistivity as a function of the boron concentration-in association with Raman spectra-and temperature-dependent transport measurements were employed. The results showed that the boron doping is the main responsible for the conductivity and that the variable range hopping (VRH) mechanism dominates the transport in these doped diamond films.
2005-12-15
The usual weekly laboratory experiment for the upper-division modern physics lab was replaced with a theme of studying diamond films grown on natural diamond. The diamonds were grown at University of Alabama at Birmingham and were studied at university physics laboratories at UAB, Alabama A and M University, University of the South, and University of North Texas. Undergraduate students measured the molar fraction of {sup 13}C in diamond films grown by a microwave-assisted chemical vapor deposition process on <1 1 0> oriented diamond plates. The molar fraction of {sup 13}C for all diamond films except the 100% and 1% was determined from Rutherford backscattering measurements at 150{sup o}. Raman scattering of a 514.5 nm Ar-ion laser beam from the same diamond films provided empirical determination of the molar fraction of {sup 13}C of the diamond films. Results from these measurements show good agreement between the nominal gas flows, Rutherford scattering, and empirical Raman determinations of the {sup 13}C molar fractions. This work took 10 lab periods and a long weekend.
Fabrication of single nickel-nitrogen defects in diamond by chemical vapor deposition
2004-11-10
Fabrication of single nickel-nitrogen (NE8) defect centers in diamond by chemical vapor deposition is demonstrated. Under continuous-wave 745 nm laser excitation single defects were induced to emit single photon pulses at 797 nm with a linewidth of 1.5 nm at room temperature. Photon antibunching of single centers was demonstrated using a Hanbury-Brown and Twiss interferometer. Confocal images revealed approximately 10^6 optically active sites/cm^2 in the synthesized films. The fabrication of an NE8 based single photon source in synthetic diamond is important for fiber based quantum cryptography. It can also be used as an ideal point-like source for near-field optical microscopy.
The versatility of hot-filament activated chemical vapor deposition
2006-11-23
In the field of activated chemical vapor deposition (CVD) of polycrystalline diamond films, hot-filament activation (HF-CVD) is widely used for applications where large deposition areas are needed or three-dimensional substrates have to be coated. We have developed processes for the deposition of conductive, boron-doped diamond films as well as for tribological crystalline diamond coatings on deposition areas up to 50 cm x 100 cm. Such multi-filament processes are used to produce diamond electrodes for advanced electrochemical processes or large batches of diamond-coated tools and parts, respectively. These processes demonstrate the high degree of uniformity and reproducibility of hot-filament CVD. The usability of hot-filament CVD for diamond deposition on three-dimensional substrates is well known for CVD diamond shaft tools. We also develop interior diamond coatings for drawing dies, nozzles, and thread guides. Hot-filament CVD also enables the deposition of diamond film modifications with tailored properties. In order to adjust the surface topography to specific applications, we apply processes for smooth, fine-grained or textured diamond films for cutting tools and tribological applications. Rough diamond is employed for grinding applications. Multilayers of fine-grained and coarse-grained diamond have been developed, showing increased shock resistance due to reduced crack propagation. Hot-filament CVD is also used for in situ deposition of carbide coatings and diamond-carbide composites, and the deposition of non-diamond, silicon-based films. These coatings are suitable as diffusion barriers and are also applied for adhesion and stress engineering and for semiconductor applications, respectively.
The structural properties of BO codoped diamond films
2009-01-01
Using Raman spectroscopy and positron annihilation technology (PAT), we investigate the structural properties of the codoped samples by implanting boron and oxygen ions into the intrinsic diamond films (called BO series) and by implanting oxygen ions into the diamond films doped with small amounts of boron in chemical vapor deposition (called CVDBO series). It is found that after 1000C annealing, the full width at half maximum (FWHM) value of diamond peak in Raman spectrum reduces, the amount of diamond increases above 99.6% and the stress changes from compression to tension. More important, the FWHM value in CVDBO series decreases by 1.6cm 1 after 1000C annealing, which is larger than that in the BO series with a decrease of 0.2cm 1, showing that the annealing prefers to...
2010-01-01
The tribological behaviors of diamond and diamond-like carbon (DLC) films play a major role on their machining and mechanical applications. In this study, diamond and diamond-like carbon (DLC) films are deposited on the cobalt cemented tungsten carbide (WC-Co) substrate respectively adopting the hot filament chemical vapor deposition (HFCVD) technique and the vacuum arc discharge with a graphite cathode, and their friction properties are evaluated on a reciprocating ball-on-plate tribometer with counterfaces of silicon nitride (Si3N4) ceramic, cemented tungsten carbide (WC) and ball-bearing steel materials, under the ambient air without lubricating condition. Moreover, to evaluate their cutting performance, comparative turning tests are conducted using the uncoated WC-Co and as-fabricated ...
Controlled synthesis of diamond and carbon nanotubes on Ni-base alloy
2008-01-01
A Ni-base alloy Inconel 600 has been used as substrate for growing two typical carbon thin film materials, diamond and carbon nanotubes (CNTs), in a hot filament chemical vapor deposition reactor with methane-hydrogen mixture. Under typical deposition conditions, the deposits formed on the as-polished alloy substrate comprise duplex layers, outer diamond layer and intermediate graphite layer. An Al thin film applied as an interlayer on the Inconel alloy effectively prevented the growth of intermediate graphite, and only a dense, adherent diamond film was deposited. When the substrate was negatively biased, a glow discharge was initiated and aligned carbon nanotubes were exclusively synthesized. No diamond was formed in this case
Tribological properties of undoped and boron-doped nanocrystalline diamond films
2009-11-28
Full Text Available.Undoped and boron-doped nanocrystalline (NCD) diamond films were deposited on mirror polished Ti–6Al–4V substrates in a Microwave Plasma Assisted Chemical Vapor Deposition system. Sliding wear tests were conducted in ambient air with a nanotribometer. A systematic study of the tribological properties for both undoped and boron-doped NCD films were carried out. It was found for diamond/diamond sliding, coefficient of friction decreases with increasing normal loads. It was also found that the wear rate of boron-doped NCD films is about 10 times higher than that of undoped films. A wear rate of ~5.2×10
Field emission properties of the globe-like diamond microcrystalline aggregate films grown by MPCVD
2010-01-01
The globe-like diamond microcrystalline aggregate films were fabricated by microwave plasma chemical vapor deposition (MPCVD) method and the field emission properties were investigated using a diode structure in vacuum. It was found that the films had a complex structure with globe-like microcrystalline diamond aggregations grown on the a-C surface and these films exhibited good electron emission properties and stability. The turn-on field of 1.1 V/mum and the current density of 6.6 mA/cm2 were obtained for these diamond microcrystalline aggregate films at the electric field of 2.73 V/mum
Characterization of polycrystalline diamond thin films grown on various substrates
1992-05-15
Polycrystalline diamond thin films have been selectively grown on various substrates such as silicon, silicon nitride, silicon dioxide, alumina, molybdenum, and boron nitride. This has been achieved by selectively damaging the substrate by an ultrasonic agitation process using diamond particles (typical size approximately 90 {mu}m) in methanol. Microwave plasma-assisted chemical vapor deposition is used to grow diamond thin films using a gas mixture of hydrogen and methane. The films were analyzed for morphology by scanning electron microscopy, chemical nature by Raman spectroscopy, and adhesion strength by z-axis pull stud testing. Films grown on boron nitride were characterized by X-ray diffraction. (orig.).
Effect of hydrogen on the properties of polycrystalline diamond thin films
1994-05-01
Microwave plasma-assisted chemical vapor deposition has been used to grow undoped and doped diamond on molybdenum and silicon substrates. Current-voltage (I-V) characteristics, secondary electron emission and depth profiles for various elements by secondary ion mass spectrometry of diamond films have been measured before and after annealing in nitrogen gas at 425 C. We have analyzed the films for morphology and chemical nature by scanning electron microscopy and Raman spectroscopy respectively. Hydrogen present in the as-deposited diamond films resulted in a decrease in the electrical resistivity and an increase in secondary electron yield. Furthermore, we have observed an increase in resistivity and decrease in yield on annealing. Comparison of these results is presented in this paper. (orig.)
Deposition of cubic boron nitride films on diamond-coated WC:Co inserts
2009-01-01
Cubic boron nitride (cBN) thin films were deposited on diamond-coated tungsten carbide (WC) cutting inserts using electron cyclotron resonance (ECR) microwave plasma chemical vapor deposition (MPCVD). The effects of gas flow rate and substrate bias on the phase composition and structure of the BN films deposited on diamond surfaces were studied. It was revealed that both the cubic phase formation and the selective etching of hexagonal phase were controlled by modulating the hydrogen and boron trifluoride flow rate ratio. By the trial and error method the gas flow rate ratio and substrate bias voltage were optimized. Moreover the phase composition of the BN film was found to be affected by the thickness of diamond buffer layer and interrelated to the effective substrate bias. The hardness o...
2009-01-01
The low temperature (5 K) photoluminescence (PL) of silicon substrate in the range of 0.8-1.12 eV before and after microwave plasma assisted chemical vapor deposition of polycrystalline diamond films was studied. The diamond films were deposited onto the pure (rhoapprox3 kOhm cm) dislocation-free silicon treated by mechanical polishing (MP) or by superior chemical-mechanical polishing (CMP). In the PL spectra of coated silicon substrates treated by CMP, the D1 and D2 lines related to the dislocation emission were registered. We suppose that the formation of dislocations in the substrate is caused by a strong adhesion of diamond film and as a consequence by the formation of inner tensions released as dislocations
The low temperature (5 K) photoluminescence (PL) of silicon substrate in the range of 0.8-1.12 eV before and after microwave plasma assisted chemical vapor deposition of polycrystalline diamond films was studied. The diamond films were deposited onto the pure (??3 kOhm cm) dislocation-free silicon treated by mechanical polishing (MP) or by superior chemical-mechanical polishing (CMP). In the PL spectra of coated silicon substrates treated by CMP, the D1 and D2 lines related to the dislocation emission were registered. We suppose that the formation of dislocations in the substrate is caused by a strong adhesion of diamond film and as a consequence by the formation of inner tensions released as dislocations.
Measurement of electron affinity in boron-doped diamond from capacitance spectroscopy
1997-05-01
Boron-doped diamond film sample has been grown on (100) silicon substrate using the microwave enhanced chemical vapor deposition method. It is found that the sample has very good material qualities and an excellent (100) surface morphology. Au/diamond Schottky was fabricated on the (100) surface to study electron affinity of the diamond sample. By measuring frequency dependence capacitance{endash}voltage spectroscopy of the Schottky sample in high vacuum and at room temperature, a very small electron affinity of about 0.025 eV and a work function of about 5.165 eV have been obtained for the (100) surface of the diamond sample supposing the diamond band gap energy is 5.5 eV. {copyright} {ital 1997 American Institute of Physics.}
2010-01-01
Device-quality self-standing diamond films have been fabricated by growing sufficiently thick homoepitaxial films on high-pressure/high-temperature-synthesized (HPHT) Ib-type (001) and vicinal (001) diamond substrates with the microwave-plasma chemical-vapor-deposition (CVD) method. The HPHT substrates used were separated from the homoepitaxial layers with a laser cutting technique. Higher-quality thick films were more successfully obtained in the case of the vicinal substrates, compared with the case of the substrate without substantial off-angle, indicating advantages of vicinal (001) Ib substrates. In room-temperature cathodoluminescence (CL) spectra taken on both sides of the self-standing diamond films thus fabricated, strong free-exciton emissions were observed even at room temperatu...
Heteroepitaxial diamond formed on silicon wafer observed by high resolution electron microscopy
1995-09-01
Diamond films with high preferential orientation (111) on silicon (100) crystalline orientation substrates had been obtained by hot-filament chemical vapor deposition (HF-CVD) method. X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman spectroscopy, and high-resolution cross-sectional transmission electron microscopy (HREM) are used to characterize the structure and morphology of the synthesized diamond films. Diamond (111) plans had been local grown epitaxially on the Si(100) substrate observed by HREM. SEM photographs show that plane diamond crystals have been obtained.
Real-time and spectroscopic ellipsometry characterization of diamond and diamond-like carbon
1989-12-10
Recent advantages in real-time and spectroscopic ellipsometry characterization of vapor-deposited thin film diamond, diamond-like carbon, and their synthesis are reviewed. Examples are presented in which ellipsometric techniques have led to insights into growth mechanisms and film structure that would have been difficult to elicit by other methods. The determination of the bulk and interface optical properties of diamond-like films in real time and the application of the techniques to obtain reproducibly tailored interfaces are demonstrated. Real-time ellipsometry has also been used to survey preparation parameter space and establish conditions that lead to sustained film groth or etching. Spectroscopic measurements of the surface, bulk, and interface structure of assisted chemical vapor deposited diamond films will also be discussed. Ellipsometry coupled with preferential chemical etching can determine the thickness and evolution of carbide layers formed on the substrate before diamond nucleation. For microwave plasma deposition of diamond on c-Si at 980deg C, the SiC is 40 to 70 A and is present on all Si substrates studied. (orig.).
The impact of diamond nanocrystallinity on osteoblast functions
2009-01-01
Nanocrystalline diamond has been proposed as an anti-abrasive film on orthopedic implants. In this study, osteoblast (bone forming cells) functions including adhesion (up to 4h), proliferation (up to 5 days) and differentiation (up to 21 days) on different diamond film topographies were systematically investigated. In order to exclude interferences from changes in surface chemistry and wettability (energy), diamond films with nanometer and micron scale topographies were fabricated through microwave plasma enhanced chemical-vapor-deposition and hydrogen plasma treatment. Scanning electron microscopy (SEM), atomic force microscopy (AFM), Raman spectroscopy and water contact angle measurements verified the similar surface chemistry and wettability but varied topographies for all of the diamon...
Carbon monoxide sensing at room temperature via electron donation in boron doped diamond films
2010-01-01
We report room temperature detection of carbon monoxide (CO) below 100 parts per million in air using boron doped diamond films prepared by hot filament chemical vapor deposition method. Gas sensing characteristics are observed to be improved with larger grain size in the films. Sensing characteristics for 100ppm CO with response time of 30s and recovery times of ~50s at room temperature show the excellence of boron doped diamond as CO sensor material. The lowest values of response time ~5s and recovery time ~20s were observed for BDD with grain size of 1mm for 1000ppm of CO in air. The carbon monoxide sensing mechanism is attributed to electron donation to p-type boron doped diamond as a result of CO oxidation on its surface.
2008-06-02
Growth of undoped and boron-doped diamond films on quartz substrates at moderate temperature of 500 {sup o}C by microwave plasma chemical vapor deposition method was studied in terms of growth rate, surface roughness and optical transmittance. Similar density of diamond seed particles on quartz surfaces seeded mechanically before the deposition process and diamond grains within diamond films grown on those substrates is observed. The growth rate is found similar to that reported for diamond deposited on silicon substrates in the same plasma deposition system, although with substantially higher activation energy. Furthermore, increased level of dopant concentration in the gas mixture resulted in a decrease of the growth rate, while a gradual reduction of the surface roughness occurred at high dopant levels. Overall, the highest measured regular optical transmittance of the undoped diamond film on quartz was 45% at 1100 nm (including quartz absorption), whereas that of boron-doped diamond peaked 5% at 700 nm (tail absorption of boron centers)
Synthesis and field emission properties of nanocrystalline diamond/carbon nanowall composite films
2010-01-01
Nanostructured composite films consisting of almost vertically aligned graphene layers, so-called 'carbon nanowalls' (CNWs), and nanocrystalline diamond films are prepared by plasma-enhanced chemical vapor deposition. The space between the walls for the composite films is widened compared to simple CNWs by interception of in-plane continuity of the wall structures. The nucleation density of diamond is responsible for the spacing and arrangement of the walls. Field emission measurements show that the composite films have lower turn-on fields (approx1 V/mum) and larger field enhancement factors (approx4000) than simple CNWs. The results indicate that electric field screening between neighboring walls is well suppressed
Synthesis of diamond-like carbon via PECD using a streaming neutral gas injection hollow cathode
2009-01-01
A streaming neutral gas injection hollow cathode system was used to deposit diamond-like carbon films via plasma enhanced chemical vapor deposition on silicon and nickel-coated silicon substrates with acetylene and hydrogen as reactant gases. Samples were characterized using SEM and Raman spectroscopy. The work presented here aims to demonstrate the capability of the system to synthesize carbonaceous films and is starting point towards work on formation of carbon nanostructures. (author)
2000-01-17
Recent studies of field emission from diamond have focused on the feasibility of growing diamond films on glass substrates, which are the preferred choice for cost-effective, large area flat panel displays. However, diamond growth on glass requires temperatures {le} 500 C, which is much lower than the temperature needed for growing conventional microwave plasma chemical vapor deposition (CVD) diamond films. In addition, it is desirable to minimize the deposition time for cost-effective processing. The authors have grown ultrananocrystalline diamond (UNCD) films using a unique microwave plasma technique that involves CH{sub 4}-Ar gas mixtures, as opposed to the conventional CH{sub 4}-H{sub 2} plasma CVD method. The growth species in the CH{sub 4}-Ar CVD method are C{sub 2} dimers, resulting in lower activation energies and consequently the ability to grow diamond at lower temperatures than conventional CVD diamond processes. For the work discussed here, the UNCD films were grown with plasma-enhanced chemical vapor deposition (PECVD) at low temperatures on glass substrates coated with Ti thin films. The turn-on field was as low as 3 V/{mu}m for a film grown at 500 C with a gas chemistry of 1%CH{sub 4}/99%/Ar at 100 Torr, and 7 V/{mu}m for a film grown at 350 C. UV Raman spectroscopy revealed the presence of high quality diamond in the films.
2009-01-01
We have fabricated high-performance ultraviolet (UV) detectors with high-quality undoped and B-doped homoepitaxial diamond layers which were sequentially grown on a high-pressure/high-temperature-synthesized (HPHT) type-Ib (100) substrate by means of a high-power microwave-plasma chemical vapor deposition method. The detector performance measured had large quantum efficiencies due to an effective built-in current amplification function, fast temporal responses, and high UV/visible sensing ratios although the HPHT substrate used had considerable amounts of various defects inducing visible light absorptions and slow detector responses. The usefulness of the bilayer detector structure employed is discussed
Effects of substrate pretreatments on diamond synthesis for Si{sub 3}N{sub 4} based ceramics
1998-07-08
Diamond synthesis for Si{sub 3}N{sub 4} ceramics after various substrate pretreatments has been carried out by the microwave-plasma enhanced chemical vapor deposition (CVD) method using a mixture of methane and hydrogen gases. Four types of pretreatments for various substrates were performed as follows: scratching with diamond powder (I), applying O{sub 2}-C{sub 2}H{sub 2} combustion flames (II), polishing with alumina (III), and platinum vapor deposition (IV). The products deposited on the substrate were examined with micro-Raman spectroscopy, scanning electron microscopy (SEM) and an X-ray diffractometer (XRD). It was found that the application of O{sub 2}-C{sub 2}H{sub 2} flames as a pretreatment of the substrate in diamond synthesis was suitable, because a higher density of diamond nucleation could be obtained, and a film-like diamond could be formed on the surface in a shorter time than without applying them. The diamond could be synthesized on the surface for all four types of substrate pretreatments performed in the present study. The effects of the substrate pretreatments on the surface morphology of grown diamond were that a film-like diamond for (I) or (II), a particle-like diamond for (III) and a particle and/or a film-like diamond for (IV) were formed on the surface. The surface morphology of grown diamond depended very much on the substrate temperature under deposition. (orig.) 18 refs.
2007-01-01
Nanocrystalline diamond/-SiC composite film system has been realized as an interlayer for the deposition of continuous and adherent diamond thin films on W and Mo substrate materials by microwave plasma chemical vapor deposition (MWCVD) technique in a single process step using a gas mixture of H2, CH4, and tetramethylsilane [Si(CH3)4, TMS]. Continuous and high quality diamond film growth on the interlayers was clearly evident. Scanning electron microscopy, X-ray diffraction and micro Raman scattering studies have been carried out to study the surface morphology and the crystal structure of the deposited films. The composite films consist of mainly two phases that of diamond and -SiC. Content of -SiC in these films can be varied by varying the concentration of TMS in the gas phase react...
Hydrogen chemisorption on diamond surfaces. Final report
Previously we demonstrated the ability to measure submonolayer quantities of surface hydrogen on insulating glasses. The present study builds on this by examining hydrogen coverages on another insulating material: the technologically important diamond (100) surface. The information to be obtained in the present study will allow us to deduce the correct structures for the diamond (100)-(1X1) and -(2X1) surface phases and provide information on the kinetics of hydrogen desorption from the (100) surface. Such experiments are essential for a complete understanding of hydrogen surface chemistry during the chemical vapor deposition of thin diamond films. This report summarizes progress made in FY93 for measuring surface hydrogen concentrations on the diamond (100) surface. Although the available LDRD resources were insufficient to finish this study in FY93, completion of the study is planned using other resources and this detailed report as a reference.
Hydrogen chemisorption on diamond surfaces. Final report
1994-09-01
Previously we demonstrated the ability to measure submonolayer quantities of surface hydrogen on insulating glasses. The present study builds on this by examining hydrogen coverages on another insulating material: the technologically important diamond (100) surface. The information to be obtained in the present study will allow us to deduce the correct structures for the diamond (100)-(1X1) and -(2X1) surface phases and provide information on the kinetics of hydrogen desorption from the (100) surface. Such experiments are essential for a complete understanding of hydrogen surface chemistry during the chemical vapor deposition of thin diamond films. This report summarizes progress made in FY93 for measuring surface hydrogen concentrations on the diamond (100) surface. Although the available LDRD resources were insufficient to finish this study in FY93, completion of the study is planned using other resources and this detailed report as a reference.
1994-01-01
Diamond particles and films with good crystallinity were grown on a molybdenum substrate with and oxyacetylene combustion flame. The diamond deposition has been carried out at ambient atmosphere. It depends on both the O[sub 2]/C[sub 2]H[sub 2] molar ratio and the substrate temperature. Diamond quality was analyzed by scanning electron microscopy and Raman spectroscopy. This Chemical Vapor Deposition (CVD) technique is an alternative method to grow diamond protective layers on metal substrates. Author (23 refs.)
2010-01-01
Diamond with different grain sizes and nanographite films were grown on silicon and diamond substrate using 90vol.% argon in hydrogen and methane gas mixtures by hot filament chemical vapor deposition method (HFCVD). In current study, the methane volume concentration was varied from 0.125 to 2vol. % in order to estimate its effect on film morphology. The substrate temperature was varied from 550 to 850^oC by external heating independently of other CVD parameters, in order to estimate the activation energy. Characterization techniques have involved Raman spectroscopy, high resolution X-ray difractometry and scanning electron microscopy. The CHEMKIN computer package has also been used to simulate the experiments. The results obtained here indicate a single mechanism for diamond growth but wi...
Fabrication and characterization of diamond field emitter diode with built-in anode
1995-12-31
Diamond field emitter diodes with built-in anode are designed, fabricated and characterized. Boron-doped p-type polycrystalline diamond film grown by hot filament chemical vapor deposition (HFCVD) is used as an emitter material. A four mask fabrication process is employed using diamond film technology compatible with Si integrated circuit (IC) processing. Photoresist is used as a sacrificial layer to produce a vacuum gap between anode and cathode. Current versus voltage (I-V) data, measured at 10{sup -6} Torr, shows Fowler-Nordheim (F-N) field emission behavior. The current density measured at 0.2MV/cm is approximately 0.5A/cm{sup 2}.
Role of polymers in CVD growth of nanocrystalline diamond films on foreign substrates
2009-01-01
Spin coating of PVA polymer with fine grained diamond powder is used as the nucleation treatment for achieving growth of nanocrystalline diamond (NCD) thin films. The growth is realized by standard microwave plasma chemical vapor deposition (CVD). The morphology and character of deposited NCD film is strongly related to the growth temperature. The low temperature process (430degreeC) results in a growth of well-faceted continuous films. The high temperature process (830 degreeC) results in voids and openings in the layer. Addition of PVA as the interlayer between the substrate and the seeding polymer composite leads to more openings. The effect is the most pronounced at 830 degreeC. This is assigned to thermal instability of PVA and oxygen chemistry present in the early beginning of the CV...
1993-12-31
Diamond is a material with a large bandgap and a high resistivity that is suitable for gamma and X-ray detector fabrication. The diamond atomic number matches relatively well that of the biological tissues (6,7). This property allows the fabrication of dosimeter for personnel exposed to X-ray and gamma radiations. In this paper, we report the fabrication and the characterization of detectors made from polycrystalline diamond thin film deposited by plasma enhanced chemical vapor deposition (PEVCVD). This technique allows large surface and low cost diamond film fabrication. Detector response to fast Nd: Yag laser pulses was investigated. Response times in the 100 ps range were measured. Tests under low energy Bremsstrahlung X-rays (20-50 keV) have shown that diamond thin films detectors can be used for X-ray flux and dose measurements. Detectors made from 10 {mu}m thick films have a sensitivity of about 3*10{sup -10} A/V.Gy.s which could be improved by the use of the thicker films (up to 300 {mu}m). (authors). 21 refs., 6 figs.
Atomic oxygen resistant behaviors of Mo/diamond-like carbon nanocomposite lubricating films
2009-01-01
Mo doped diamond-like carbon (Mo/DLC) films were deposited on Si substrates via unbalanced magnetron sputtering of molybdenum combined with plasma chemical vapor deposition of CH4/Ar. The microstructure of the films, characterized by transmission electron microscopy and selected area electron diffraction, was considered as a nanocomposite with nano-sized MoC particles uniformly embedded in the amorphous carbon matrix. The structure, morphology, surface composition and tribological properties of the Mo/DLC films before and after the atomic oxygen (AO) irradiation were investigated and a comparison made with the DLC films. The Mo/DLC films exhibited more excellent degradation resistant behaviors in AO environment than the DLC films, and the MoC nanoparticles were proved to play a critical role of preventing the incursion of AO and maintaining the ...
1997-05-01
Diamondlike carbon (DLC) thin films have been prepared by chemical vapor deposition assisted by electron cyclotron resonance plasma at low pressure with radio frequency (rf) power applied to the substrate. The microstructure studies by transmission electron microscopy and electron energy loss spectroscopy show the existence of nanocrystalline diamond grains in DLC films prepared at 0.35 Pa. The cluster{close_quote}s size varies from 4 to 30 nm with bias voltage (V{sub b}) varying from {minus}200 to {minus}600V. A phase transition from hexagonal to cubic diamond was also observed with increasing V{sub b}. {copyright} {ital 1997 American Institute of Physics.}
1997-10-31
Distribution of defects and impurities was investigated by cathodoluminescence spectroscopy on as-grown boron-doped diamond film synthesized by microwave plasma chemical vapor deposition method. Luminescence profiles in a boron-doped diamond film were observed by cross-section CL images. Intense emission of 535 nm (--2.32 eV) band was found in a thin layer of the growth surface and in a rather thick layer of interface to the silicon substrate. Complementary to the 535-nm emission, the edge emission appeared in the bulk region excluding the surface layer. The origination of the 535-nm band can be explained by a boron-vacancy center. (orig.) 14 refs.
2010-01-01
This review focuses on a status report on the science and technology of ultrananocrystalline diamond (UNCD) films developed and patented at Argonne National Laboratory. The UNCD material has been developed in thin film form and exhibit multifunctionalities applicable to a broad range of macro to nanoscale multifunctional devices. UNCD thin films are grown by microwave plasma chemical vapor deposition (MPCVD) or hot filament chemical vapor deposition (HFCVD) using new patented Ar-rich/CH4 or H2/CH4 plasma chemistries. UNCD films exhibit a unique nanostructure with 2-5nm grain size (thus the trade name UNCD) and grain boundaries of 0.4-0.6nm for plain films, and grain sizes of 7-10nm and grain boundaries of 2-4nm when grown with nitrogen introduced in the Ar-rich/CH4 chemistry, to produce UN...
2005-01-01
Mechanical shaft seals used in pumps are critically important to the safe operation of the paper, pulp, and chemical process industry, as well as petroleum and nuclear power plants. Specifically, these seals prevent the leakage of toxic gases and hazardous chemicals to the environment and final products from the rotating equipment used in manufacturing processes. Diamond coatings have the potential to provide negligible wear, ultralow friction, and high corrosion resistance for the sliding surfaces of mechanical seals, because diamond exhibits outstanding tribological, physical, and chemical properties. However, diamond coatings produced by conventional chemical vapor deposition (CVD) exhibit high surface roughness (Ra
Voltammetric studies at the polycrystalline diamond grown over a graphite electrode material
1999-02-08
Boron-doped polycrystalline diamond thin films were grown over POCO graphite by a microwave plasma assisted chemical vapor deposition (CVD) using a gas mixture of methane and hydrogen. As-deposited films were analyzed by scanning electron microscopy (SEM) for their morphology. Cyclic voltammetry has been used to evaluate the background current response corrected for the uncompensated IR drop. Redox kinetics of ferri-ferrocyanide at the boron-doped diamond/graphite electrode has been investigated. The lowest observed peak separation was observed to be 222 mV at a scan rate of 5 mV/s. The heterogeneous electron transfer rate constant has been determined using the experimental data and a COOL algorithm. The rate constant was found to be {proportional_to}2 2 x 10{sup -4} ({alpha}=0.5 or variable) cm/s, and subsequently, the reaction kinetics was considered to be sluggish at the diamond electrode/solution interface. The diamond films grown over graphite electrode material may have uses in electrosynthesis and electroanalysis since the doped diamond films are electrically conductive and chemically inert. (orig.) 28 refs.
Optical characterization of diamond synthesis using CH3OH-H2 gas mixtures
2005-01-01
Diamond films with high infrared transmittance have been successfully deposited using CH3OH-H2 gas mixtures through microwave plasma enhanced chemical vapor deposition (MWCVD). The primary purpose of this study is to determine the effect of the deposition conditions on the optical properties of MWCVD diamond films using CH3OH-H2 gas mixtures. Room temperature optical properties of freestanding diamond films were studied by Fourier transform IR spectroscopy. Experimental results indicated that under appropriate deposition temperature (620 degree C) and methanol concentration (5.7%), the refractive index of CVD diamond films (2.33) was comparable with that of natural diamond (2.417). The average infrared transmittance was above 65% in the middle infrared region (500 cm-1-4000 cm-1), ...
1999-07-01
Chemical vapor deposition (CVD) technology affords the possibility of producing synthetic diamond film electrodes, with several advantageous properties due the unique characteristics of diamond. In this work, we present the study of boron-doped diamond films growth on molybdenum and silicon substrates, using boron trioxide as dopant in a filament assisted CVD reactor. The objective was to obtain semiconductor diamond for use as electrode. The samples were characterized by scanning electron microscopy and Raman spectroscopy to confirm morphology and doping levels. We have assembled electrodes with the various samples, Pt, Mo, Si and diamond, by utilizing brass and left as base materials. The electrodes were tested in neutralization potentiometric titrations for future use in electroanalysis. Boron-doped electrodes have very good performance compared with Pt, widely used in analytical chemistry. (author)
Electron field emission for ultrananocrystalline diamond films
2001-03-01
Ultrananocrystalline diamond (UNCD) films 0.1--2.4 {mu}m thick were conformally deposited on sharp single Si microtip emitters, using microwave CH{sub 4}--Ar plasma-enhanced chemical vapor deposition in combination with a dielectrophoretic seeding process. Field-emission studies exhibited stable, extremely high (60--100 {mu}A/tip) emission current, with little variation in threshold fields as a function of film thickness or Si tip radius. The electron emission properties of high aspect ratio Si microtips, coated with diamond using the hot filament chemical vapor deposition (HFCVD) process were found to be very different from those of the UNCD-coated tips. For the HFCVD process, there is a strong dependence of the emission threshold on both the diamond coating thickness and Si tip radius. Quantum photoyield measurements of the UNCD films revealed that these films have an enhanced density of states within the bulk diamond band gap that is correlated with a reduction in the threshold field for electron emission. In addition, scanning tunneling microscopy studies indicate that the emission sites from UNCD films are related to minima or inflection points in the surface topography, and not to surface asperities. These data, in conjunction with tight binding pseudopotential calculations, indicate that grain boundaries play a critical role in the electron emission properties of UNCD films, such that these boundaries: (a) provide a conducting path from the substrate to the diamond--vacuum interface, (b) produce a geometric enhancement in the local electric field via internal structures, rather than surface topography, and (c) produce an enhancement in the local density of states within the bulk diamond band gap.
Pressure effect of superconducting transition temperature for boron-doped diamond films
2008-09-15
The superconducting transition temperature of homoepitaxial boron-doped diamond thin films fabricated by microwave plasma-assisted chemical vapor deposition technique depend on substrate orientation. In addition, heavily doped diamond thin films indicate anisotropic lattice expansion. From these points of view, pressure effect will give us knowledge of the superconducting mechanism of boron-doped diamond. We report measurements of the electrical resistivity of heavily boron-doped diamond thin film under pressure up to P 1.45 GPa and 1.27 GPa for (1 1 1) and (1 0 0) homoepitaxial thin films, respectively. The superconducting transition temperature decreases linearly with increasing pressure by a rate of {delta}T{sub c}/{delta}P = -1.17 x 10{sup -1} K/GPa and -1.51 x 10{sup -2} K/GPa for (1 1 1) and (1 0 0) thin film, respectively.
1992-01-01
This work experimentally investigates techniques for high quality diamond synthesis and develops means for electrical and physical characterization of the films. The films are deposited by plasma assisted chemical vapor deposition using a methane/hydrogen plasma in a microwave plasma disk reactor system. Both a diamond past nucleation method and diamond powder nucleation method are studied. Although both methods produced similar quality diamond films, the powder nucleation method produced fine grain, sub-micron sized crystallite films whereas the past nucleation method produced large grain, several-micrometer size crystallite films. For powder polished films, all metallic contacts were ohmic. These samples were used to explore the high electric field properties of diamond. For fields larger than approximately 1 [times] 10[sup 5] V/cm the electrical properties are dominated by defects. For low electric fields, the electrical conductivity was constant. For high fields, the conductivity was field activated according to Poole's law. This behavior was modeled as due to ionizable defects and indicates there is approximately one ionizable defect per 10,000 host atoms. The breakdown field for these films was somewhat less than 1[times]10[sup 6] V/cm. A large concentration of defects is compatible with the observation of ohmic contact behavior regardless of metallic work function. Non-ohmic, Schottky barrier contacts were achievable on the past polished films. For Al/diamond/silicon structures diode characteristics were observed. These I-V characteristics were modeled as an ideal Schottky barrier diode in series with bulk diamond, for which the property of the bulk diamond follows an I[alpha]V[sup m] relationship, indicative of space charge limited current in an insulating material. The rectifying behavior was determined at the Al/diamond surface rather than the diamond/silicon surface. The best rectification ratios were 2 [times] 10[sup 5].
Textures and morphologies of chemical vapor deposited (CVD) diamond
1991-01-01
The textures, surface morphologies, structural perfection, and properties of diamond films grown by activated chemical vapor deposition (CVD) vary greatly with the growth conditions. The evolution of two commonly observed polycrystalline morphologies, which give rise to textures, will be described as well as the development of four films grown to produce , , and near '' textures with various combinations of growth facets. These films were grown to test models of texture development. Films free of twins, microtwins, and stacking faults are deposited when only (100) facets are permitted to grow. In polycrystalline materials, special conditions must be met to avoid the formation of planar defects at the peripheries of individual crystallites. The planar defects grow from (111) or mixed microfaceted surfaces. Twinning plays an important role in growth of (111) faceted surfaces. The films have been characterized with Raman spectroscopy, x-ray diffraction, transmission electron microscopy (TEM), scanning electron microscopy (SEM), and optical methods. 13 refs., 7 figs.
Superconductivity in CVD Diamond Thin Films Well-Above Liquid Helium Temperature
2004-01-01
Diamond has always been adored as a jewel. Even more fascinating is its outstanding physical properties; it is the hardest material known in the world with the highest thermal conductivity. Meanwhile, when we turn to its electrical properties, diamond is a rather featureless electrical insulator. However, with boron doping, it becomes a p-type semiconductor, with boron acting as a charge acceptor 1-2. Therefore the recent news of superconductivity in heavily boron-doped diamond synthesized by high pressure sintering was received with considerable surprise 3. Opening up new possibilities for diamond-based electrical devices, a systematic investigation of these phenomena clearly needs to be achieved. Here we show unambiguous evidence of superconductivity in a diamond thin film deposited by a chemical vapor deposition (CVD) method. Furthermore the onset of the superconducting transition is found to be 7.4K, which is higher than the reported value in ref(3) and well above helium liquid temperature. This finding establishes the superconductivity to be a universal property of boron-doped diamond, demonstrating that device application is indeed a feasible challenge.
2004-01-01
A multilayer structure is presented which allows the deposition of high-quality heteroepitaxial diamond films on silicon. After pulsed-laser deposition of a thin yttria-stabilized zirconia (YSZ) layer on silicon, iridium was deposited by e-beam evaporation. Subsequently, diamond nucleation and growth was performed in a chemical vapor deposition setup. The epitaxial orientation relationship measured by x-ray diffraction is diamond(001)[110] parallel Ir(001)[110] parallel YSZ(001) [110] parallel Si(001)[110]. The mosaicity of the diamond films is about an order of magnitude lower than for deposition directly on silicon without buffer layers and nearly reaches the values reported for single-crystal diamond on Ir/SrTiO3. In the effort towards single-crystal diamond wafers, the present solution offers advantages over alternative growth ...
Diamond thin films grown by microwave plasma assisted chemical vapor deposition
1991-09-05
Undoped and boron doped diamond thin films have been successfully grown by microwave plasma chemical vapor deposition from CH{sub 4}, H{sub 2}, and B{sub 2}H{sub 6}. The films were characterized using x- ray diffraction techniques, Raman and infrared spectroscopies, scanning electron microscopy, secondary ion mass spectrometry, and various electrical measurements. The deposition rates of the diamond films were found to increase with the CH{sub 4} concentration, substrate temperature, and/or pressure, and at 1.0% methane, 900{degrees}C, and 35 Torr, the value was measured to be 0.87 {mu}m/hour. The deposition rate for boron doped diamond films, decreases as the diborane concentration increases. The morphologies of the undoped diamond films are strongly related to the deposition parameters. As the temperature increases from 840 to 925 C, the film morphology changes from cubo-octahedron to cubic structures, while as the CH{sub 4} concentration increases from 0.5 to 1.0%, the morphology changes from triangular (111) faces with a weak preferred orientation to square (100) faces. At 2.0% Ch{sub 4} or higher the films become microcrystalline with cauliflower structures. Scanning electron microscopy analyses also demonstrate that selective deposition of undoped diamond films has been successfully achieved using a lift-off process with a resolution of at least 2 {mu}m. The x-ray diffraction and Raman spectra demonstrate that high quality diamond films have been achieved. The concentration of the nondiamond phases in the films grown at 1.0% CH{sub 4} can be estimated from the Raman spectra to be at less than 0.2% and increases with the CH{sub 4} concentration. The Raman spectra of the boron doped diamond films also indicate that the presence of boron tends to suppress the nondiamond phases in the films. Infrared spectra of the undoped diamond films show very weak CH stretch peaks which suggest that the hydrogen concentration is very low.
Growth of diamond thin films on nickel-base alloys
1996-02-01
Microwave plasma-assisted chemical vapor deposition has been employed to grow diamond films (thickness up to 50 {mu}m) using a gas mixture of hydrogen (H{sub 2}), methane (CH{sub 4}), and oxygen (O{sub 2}) on various substrates such as Ni 200, MONEL 400, INCONEL 600, INVAR, single crystal nickel with orientations of (100), (111), (110), etc. Nucleation of diamond on the substrates has been achieved by seeding with diamond particles, manual scratching, and ultrasonic agitation in methanol (CH{sub 3}OH) containing diamond particles. The substrate underwent H{sub 2} microwave plasma treatment for 5-60 min to remove any oxide film present prior to diamond growth. Growth of diamond over MONEL 400 was achieved at various CH{sub 4} concentrations in H{sub 2}. As-deposited films were analyzed by scanning electron microscopy (SEM), Raman spectroscopy, secondary ion mass spectroscopy, X-ray photoelectron spectroscopy and Auger electron spectroscopy. According to SEM the morphology of the grown films was (100) texture over the entire surface (<0.5 cm{sup 2}) of Ni 200 substrate. Raman analysis of the top side of deposited film confirms for diamond and on the back side of the free-standing film shows the characteristic peaks for diamond and graphite. As-deposited films were diamond and other forms of non-diamond carbon on INCONEL 600 and on INVAR. (orig.)
2001-04-01
Cubic boron nitride (c-BN) crystals about 0.1-0.3 mmin dimension were treated with iron carbide powders (high purity 99%) with size of 80-100 mesh at a high temperature of 1620 K and a high pressure of 5.2 GPa. It was found that hetero-epitaxial diamond films have been grown on the c-BN from iron carbide. The formation of dia-mond films on the cubic boron nitride can be confirmed by laser Raman spectra, face scan of elements and reflective high-energy electron diffraction. It was suggested that diamond films could be epitaxially formed on the c-BN through decomposition of iron carbide. This approach provides a possible and very effective way to realize hetero-epitaxial growth of homogeneous and large-area diamond films on c-BN, which is different from the conventional technique using a chemical vapor deposition method. (orig.)
Thermal stability evaluation of diamond-like nanocomposite coatings
2003-06-23
Diamond-like nanocomposite (DLN) is a class of modified diamond-like carbon (DLC) coatings. The DLN films consist of amorphous networks of carbon and silicon, which are made by incorporating the Si-O structures into the DLC films. The thermal stability of DLN films was investigated by annealing the films deposited on Si (1 0 0) substrates by plasma enhanced chemical vapor deposition. The films were heated in ambient air for 1 h at the annealing temperatures ranging from 200 to 600 deg. C. The mechanical properties as well as structural modification of the annealed films were investigated as a function of annealing temperature. The chemical structure, composition, thickness and hardness values of the annealed films were measured by Raman spectrometer, electron probe micro analyzer, scanning electron microscope and ultra micro-indentation system, respectively. The comparison between DLN and DLC films on their thermal stability was made in order to understand the characteristics of DLN films. It is assumed that the DLN films show a good thermal stability for the protective coating applications at high temperature environment in air atmosphere in comparison with DLC films.
Oxygen plasma etching of silver-incorporated diamond-like carbon films
2009-01-01
Diamond-like carbon (DLC) film as a solid lubricant coating represents an important area of investigation related to space devices. The environment for such devices involves high vacuum and high concentration of atomic oxygen. The purpose of this paper is to study the behavior of silver-incorporated DLC thin films against oxygen plasma etching. Silver nanoparticles were produced through an electrochemical process and incorporated into DLC bulk during the deposition process using plasma enhanced chemical vapor deposition technique. The presence of silver does not affect significantly DLC quality and reduces by more than 50% the oxygen plasma etching. Our results demonstrated that silver nanoparticles protect DLC films against etching process, which may increase their lifetime in low earth o...
Investigation of a-C:F films as hydrogenated diamond-like carbon and low-k materials
2005-03-22
Fluorinated amorphous carbon films were deposited on a p-type silicon substrate by using an inductively coupled plasma chemical vapor deposition with mixture of carbon tetrafluoride and methane gases. The structural properties of fluorinated amorphous carbon films as a diamond-like carbon were studied by Raman spectra, Fourier transform infrared spectra (FTIR) and X-ray photoelectron spectroscopy (XPS) spectra as a function of the flow rate ratio of precursors. The variation of the fluorine contents of fluorinated amorphous carbon films was investigated by X-ray photoelectron spectroscopy. From these chemical results, the correlation between the dielectric constant and the variation of the bonding structure as a function of the flow rate ratio was researched.
Improvements in CVD/CVI processes for optimizing nanocrystalline diamond growth into porous silicon
2010-01-01
This paper reports a novel procedure to infiltrate nanocrystalline diamond films (NCD) on porous silicon (PS) substrate. The NCD/PS films resulted in a composite material, with great potential for electrochemical application, mainly due to its high active surface area. The Hot Filament Chemical Vapor Deposition reactor was changed to Hot Filament Chemical Vapor Infiltration reactor in order to grow NCD films infiltrated into deep holes of PS substrate. This procedure allowed the infiltration of the reacting gases into the porous structure where the nucleation takes place, followed by the coalescence and film formation at pore bottoms and walls. In this configuration an additional entrance of CH4 was located next to the PS substrate using two distinct positions called ''underneath'' and ''a...
The thermal stability of nanocrystalline diamond films with 10-30 nm grain size deposited by microwave enhanced chemical vapor deposition on silicon substrate was investigated as a function of annealing temperature up to 1200 C. The thermal stability of the surface-upper atomic layers was studied with near edge x-ray absorption fine structure (NEXAFS) spectroscopy recorded in the partial electron yield mode. This technique indicated substantial thermally induced graphitization of the film within a close proximity to the surface. While in the bulk region of the film no graphitization was observed with either Raman spectroscopy or NEXAFS spectroscopy recorded in total electron yield mode, even after annealing to 1200 C. Raman spectroscopy did detect the complete disappearance of transpolyacetylene (t-PA)-like ?1 and ?3 modes following annealing at 1000 C. Secondary ion mass spectroscopy, applied to investigate this relative decrease in hydrogen atom concentration detected only a ~30% decrease in the bulk content of hydrogen atoms. This enhanced stability of sp3 hybridized atoms within the bulk region with respect to graphitization is discussed in terms of carbon bond rearrangement due to the thermal decomposition of t-PA-like fragments.
Understanding the chemical vapor deposition of diamond: recent progress
2009-01-01
In this paper we review and provide an overview to the understanding of the chemical vapor deposition (CVD) of diamond materials with a particular focus on the commonly used microwave plasma-activated chemical vapor deposition (MPCVD). The major topics covered are experimental measurements in situ to diamond CVD reactors, and MPCVD in particular, coupled with models of the gas phase chemical and plasma kinetics to provide insight into the distribution of critical chemical species throughout the reactor, followed by a discussion of the surface chemical process involved in diamond growth
Influence of Humidity on Microtribology of Vertically Aligned Carbon Nanotube Film
2007-03-28
The aim of this study is to probe the influence of water vapor environment on the microtribological properties of a forestlike vertically aligned carbon nanotube (VACNT) film, deposited on a silicon (001) substrate by chemical vapor deposition. Tribological experiments were performed using a gold tip under relative humidity varying from 0 to 100%. Very low adhesion forces and high friction coefficients of 0.6 to 1.3 resulted. The adhesion and friction forces were independent of humidity, due probably to the high hydrophobicity of VACNT. These tribological characteristics were compared to those of a diamond like carbon (DLC) sample.
Effect of boron doping on the surfaces of diamond thin films
1993-05-01
Auger and electron energy loss spectroscopies were used to study chemical and structural properties of as-grown surfaces of boron-doped diamond thin films prepared by microwave plasma-assisted chemical vapor deposition. Results are compared to surface properties of as-deposited undoped diamond thin films. As the boron level in the film increased energy losses associated with [pi] electron bonds ([ital sp][sup 2] sites) were enhanced at the surface. Similarly, the surface oxygen level of the films increased with increasing boron content. On the other hand the characteristic diamond Raman peak at 1332 cm[sup [minus]1] was narrower than in the undoped films and the broad band at about 1500 cm[sup [minus]1] associated with nondiamond carbon decreased. Surface morphology micrographs obtained from scanning electron microscopy (SEM) measurements indicated that the introduction of boron enhances the appearance of the (111) planes. Surface characterization together with the Raman and SEM results suggest that boron doping enhances surface reactivity resulting in increased adsorption of oxygen and carbonaceous species following the growth process. This behavior has implications on surface treatments necessary for device applications.
1995-12-31
A high-quality, low-stress 200 {mu}m epitaxial diamond film has been grown on a 400 {mu}m thick high-temperature-high-pressure Ha diamond. X-ray diffraction images of the film indicate that a large region of the film is fairly defect free and individual dislocations have been imaged in this region. Depth-resolved Raman results indicate that the region of the film with a low density of defects also has lower stress than in the higher defect density region. Transient photoconductivity measurements were performed on the high and low line defect density regions of the homoepitaxial diamond film to determine the effects of the stress and defect density on the combined electron-hole mobility and carrier lifetime. The correlation between the electrical properties and the x-ray diffraction imaging suggests that line defects may not be the limiting factor in the carrier transport at the present film quality.
1999-01-01
The DOE has been supporting Professor Chang and his students in the area of plasma and photon synthesis of diamond-like and ceramic films with varying complexity during the past three years. We have made substantial contribution to the field during this period of time. Some of the important questions have been addressed, and they include: a. How does the energy (wavelength) of the laser change the composition and energy distribution of the ablated species? b. How do surface mobility and the intensity of the plasma plume affect crystal nucleation and growth? c. How can one manipulate the system parameters during film growth to achieve special properties for unique applications? In the area of photon synthesis, we have shown that amorphous diamond films can have properties very similar to polycrystalline diamond films and yet they may have wider applications in such areas as coating and electronics. For example, we have shown that these films can be used to protect plastics such as polycarbonate surfaces. During the course of our amorphous diamond films research, we have also identified important parameters which alter the film properties. Higher photon energy and laser power density contribute to higher percentage of carbon ion density and energy in the plasma plume. This in turn proves films with higher percentage of diamond-like sp{sup 3} bonds and thus diamond-like properties of the films. Lower photon energies and collision of the plasma plume with background gas will produce films which are rich in graphitic properties. In the area of oxide film growth, we have found, in general, that better crystalline films can be grown by laser ablation at much lower substrate temperatures than by chemical vapor deposition process. This is due to the fact that in laser ablation the depositing species have more kinetic energies and the whole process involves rapid solidification. By using optical emission spectroscopy, we have learned how to adjust the deposition parameters to control film properties such as grain size and crystal orientations. These control capabilities have allowed us to grow oxide films with unique properties, such as high optical nonlinearity. In addition, we have been able to grow films with special crystalline orientations to serve as templates for chemical vapor deposition processes.
Piezoresistive gauge factor of polycrystalline diamond measured at different fields and temperatures
1995-12-31
The gauge factor of boron-doped diamond films grown on oxidized Si substrates by hot filament chemical vapor deposition (CVD) reactor was measured by the cantilever beam method. For an annealed film, the gauge factor increases strongly with electric field only in the range of 411-611V/cm. Interestingly, the zero-stress resistivity decreases strongly in this range. Such an increase in gauge factor is not found for an un-annealed film. The field-dependence of gauge factor is reported for the first time. The gauge factor was also measured in the temperature range of 22-80{degrees}C for two samples with different doping levels. Preliminary results suggest that the increase of gauge factor with temperature is prominent only for high resistivity.
Examination of diamond growth precursor dependance in an electron cyclotron resonance plasma system
1995-12-31
We have investigated the deposition of diamond films at relatively low substrate temperatures using an electron cyclotron resonance (ECR) enhanced plasma chemical vapor deposition (CVD) system. Films were separately deposited in a hydrogen ambient from methanol and methane precursor species in the pressure regime of 1.0 Torr. Oxygen was independently added to maintain consistent C/H/O atomic ratios The effect of growth system parameters such as gas composition, temperature, and input microwave power on resultant film morphology was examined using SEM. Structural quality was assessed using X-ray diffraction and Raman spectroscopy. Comparisons were made between growth systems with the same C/H/O atomic ratios for crystalline quality, growth rate, and morphology.
Antibacterial activity of fluorinated diamond-like carbon films produced by PECVD
2010-01-01
Diamond-like carbon (DLC) films have been the focus of extensive research in recent years due to its potential application as surface coatings on biomedical devices. It has been already reported that fluorine (F) could increase DLC antibacterial activity. In this paper we investigated the antibacterial activity of fluorinated-DLC (F-DLC) films with various F contents and its correlation with bacterial adhesion mechanism according to thermodynamic theory. F-DLC was grown on a 316L stainless steel substrate using plasma enhanced chemical vapor deposition (PECVD) by varying the ratio of carbon tetrafluoride and methane. The antibacterial tests were performed against E. coli and the influence of F content on composition, surface energy, stress and surface roughness was also investigated. As F ...
2010-01-01
Growth orientation, crystalline structure, boron-doping distribution, and residual stresses of freestanding boron-doped chemical-vapor-deposited (CVD) diamond films have been comprehensively investigated. The introducing boron source of trimethylborate (B(OCH3)3) in a doping level region favorably leads to a predominant [110] texture growth. By analyzing the asymmetry parameter q related to Fano-type interference obtained from micro-Raman spectroscopy, it is qualitatively deduced that the boron concentration in the films is spatially inhomogeneous in a large scale, either on the growth surface (between different grain facets and boundaries) or along the cross-section. The boron distribution on the cross-section is attributed to the increase of growing temperature on top surface and, conseq...
Barriers to the nucleation of methyl groups on the diamond (111) surface
Questions about the mechanism of diamond film growth by low-pressure, plasma-assisted chemical vapor deposition methods have persisted for some time now. As an attempt to explore one aspect of the problem, we examine the energetics of several adsorbed diamond (111) surfaces. The adsorbates are mixtures of methyl groups and hydrogen atoms. The model for these systems is the molecular orbital hamiltonian of Dewar and coworkers. From these calculations we find that H adsorbtion is preferred due both to bond energy and steric effects. Thus nucleation of a cluster of three or more methyl groups, as assumed in earlier work, is energetically very demanding. 6 refs., 3 figs.
Barriers to the nucleation of methyl groups on the diamond (111) surface
1989-01-01
Questions about the mechanism of diamond film growth by low-pressure, plasma-assisted chemical vapor deposition methods have persisted for some time now. As an attempt to explore one aspect of the problem, we examine the energetics of several adsorbed diamond (111) surfaces. The adsorbates are mixtures of methyl groups and hydrogen atoms. The model for these systems is the molecular orbital hamiltonian of Dewar and coworkers. From these calculations we find that H adsorbtion is preferred due both to bond energy and steric effects. Thus nucleation of a cluster of three or more methyl groups, as assumed in earlier work, is energetically very demanding. 6 refs., 3 figs.
Novel processes have been developed to selectively grow polycrystalline diamond on various substrates (Si, SiO2, Al2O3, Si3N4, BN, sapphire, Mo, and Ta) using a gas mixture of CH4 and H2 by high pressure microwave plasma-assisted chemical vapor deposition (HPMACVD). This has been achieved by selectively damaging the substrates by ultrasonic agitation using diamond particles in methanol. Microstructures of doped and undoped polycrystalline diamond have been fabricated on bare Si substrates as well as on oxidized Si substrates for microelectronic applications. The doping source for boron and phosphorus are B2O3 (and other oxides) and P2O5 (and other oxides), respectively. The films are analyzed by SEM, SIMS (dopant identification and depth profiling), current-voltage measurements, Raman spectroscopy, optical micrography, and wavelength-dispersive spectrometry. The effects of annealing and hydrogen microwave plasma treatment on the resistivity of doped and undoped polycrystalline diamond thin films and on their morphology are described.
In/extrinsic granularity in superconducting boron-doped diamond
When charge carriers are introduced in diamond, e.g. by chemical doping with Boron (B), the C1-x?1021cm-3), diamond becomes superconducting. Using microwave plasma-assisted chemical vapor deposition (MPCVD) we have prepared diamond:B thin films with critical offset temperatures T below 3 K. We have investigated the transport properties of these diamond:B thin films, which show pronounced granular effects. It turns out, that this granularity is both intrinsic as well as extrinsic. The extrinsic granularity is the effect of the growth method which needs to start from a seeding of the substrate with detonation nanodiamond, which acts as nucleation centers for further MPCVD growth of the film. In using SPM/STM techniques, we also observed intrinsic granularity, meaning that within physical grains, we observe also a strong intragrain modulation of the order parameter. As a consequence of these granularities, the transport properties show evidence of (i) strong superconducting fluctuations and (ii) Cooper pair tunneling and/or quasiparticle tunneling. The latter effects explain the observed negative magnetoresistance.
Naval research laboratory takes a close look at unique diamonds
2010-03-23
Naval Research Laboratory, which has been involved in pioneering work involving chemical vapor deposition of diamond and the use of diamond materials in advanced technologies relevant to the US Department of Defense ...
Short Pulse Laser Production of Diamond Thin Films
1998-03-20
The use of diamond thin films has the potential for major impact in many industrial and scientific applications. These include heat sinks for electronics, broadband optical sensors, windows, cutting tools, optical coatings, laser diodes, cold cathodes, and field emission displays. Attractive properties of natural diamond consist of physical hardness, high tensile yield strength, chemical inertness, low coefficient of friction, high thermal conductivity, and low electrical conductivity. Unfortunately, these properties are not completely realized in currently produced diamond thin films. Chemical vapor deposition, in its many forms, has been the most successful to this point in producing crystalline diamond films microns to millimeters in thickness which are made up of closely packed diamond crystals microns in physical dimension. However, high purity films are difficult to realize due to the use of hydrogen in the growth process which becomes included in the film matrix. These impurities are manifest in film physical properties which are inferior to those of pure crystalline diamond. In addition, the large density of grain boundaries due to the polycrystalline nature of the films reduce the films' diamond-like character. Finally, substrates must be heated to several hundred degrees Celsius which is not suitable for many materials. Pulsed laser deposition is attractive due to its ability to produce high purity films-limited only by the purity of the target. For diamond film production, high purity carbon can be ablated directly by lasers and deposited as thin films at ambient temperatures. However, lasers currently in use generally deliver long (>10 ns) pulses, and the generally explosive nature of laser ablation, in addition to the desired single-atom or single-ion carbon, liberates significant amounts of carbon clusters (C{sub n} where n=2-30) and macroscopic particles (> 1-10 pm) of carbon. These carbon particles interrupt the ordered deposition of crystalline diamond, forming undesirable grain boundaries and rough surfaces that are difficult to polish. In addition, PLD generated films tend to be ''amorphous'' or nanocrystalline with no observable long-range order, but still possessing physical properties which are diamond-like in some approximation. This has given rise to the term ''diamond-like carbon'' when referring to these PLD-produced, amorphous carbon films. Growth rates for PLD have been prohibitively slow until recently with the advent of high average power, high rep-rate lasers.
Diamond chemical vapor deposition on optical fibers for fluorescence waveguiding
2004-11-10
A technique has been developed for depositing diamond crystals on the endfaces of optical fibers and capturing the fluorescence generated by optically active defects in the diamond into the fiber. This letter details the diamond growth on optical fibers and transmission of fluorescence through the fiber from the nitrogen-vacancy (N-V) color center in diamond. Control of the concentration of defects incorporated during the chemical vapor deposition (CVD) growth process is also demonstrated. These are the first critical steps in developing a fiber coupled single photon source based on optically active defect centers in diamond.
Friction and wear properties of diamonds and diamond coatings
1991-01-01
The recent development of chemical vapor deposition techniques for diamond growth enables bearings to be designed which exploit diamond's low friction and extreme resistance to wear. However, currently produced diamond coatings differ from natural diamond surfaces in that they are polycrystalline and faceted, and often contain appreciable amounts of non-diamond material (i.e. graphitic or amorphous carbon). Roughness, in particular, influences the friction and wear properties. Rough coatings severely abrade softer materials, and can even wear natural diamond sliders. Nevertheless, the best available coatings exhibit friction coefficients as low as those of natural diamond and are highly resistant to wear. This paper reviews the tribological properties of natural diamond, and compares them with those of chemical vapor deposited diamond coatings. Emphasis is ...
Thermoluminescence of chemical-vapor-deposited diamond film irradiated with X-rays
Diamond film was synthesized by using chemical-vapor deposition (CVD). Three-dimensional thermoluminescence (TL) spectrum of the CVD diamond film irradiated with X-rays showed one TL peak at 430 nm around 560 K. The glow curve of the CVD diamond film produced one dominant 500-K peak that was caused by first-order kinetics. The activation energy and the escape frequency of the 560-K glow curve were calculated to be 0.92 approx 1.05 eV and 1.34x10 sup 7 sec sup - sup 1 , respectively. The emission spectrum at 560 K was split into 1.63-eV, 2.60-eV, and 3.07-eV emission bands. The 1.63-eV emission band is known to be attributable to silicon-vacancy center. Also, the 2.60-eV and the 3.07-eV emission bands were found to be associated with the A center and the H3 center, respectively.
2010-01-01
A MSM (metal-semiconductor-metal) ultraviolet (UV) photo-detector was fabricated on a high-quality diamond film deposited by microwave chemical vapor deposition on a Si substrate. Charge-based deep level transient spectroscopy (Q-DLTS) was used for obtaining the information on activation energy (Ea), capture cross section (s) and concentration (Nt) of trapping centers in the band gap of the diamond film. A shallow level with Ea = 0.213 eV, s = 9.88 x 10-20 cm2 and Nt = 1.1 x 1011 cm-2 is present in the diamond film. The shallow level may not act as effective recombination center due to the so small activation energy according to the Schockly-Read-Hall statistics. The UV photo-detector presents slow time response, high responsivity and high photoconductive gain under irradiation of 220 nm m...
1995-07-01
High-resolution transmission electron microscopy (HRTEM) has been used to investigate the microstructure of diamond films grown by plasma-assisted chemical vapor deposition using fullerene precursors. HRTEM observations of as-grown films revealed an array of larger crystals (>200 nm) within a polycrystalline matrix of much smaller crystallites ( orientations with respect to the Si (100) substrate and showed evidence of structural defects on the periphery of the crystals. The most common defects were V-shaped {Sigma}9 twin boundaries, which are generally believed to serve as re-entrant sites for diamond nucleation and growth. The observation of growth steps on both (111) and (110) surfaces seems to support a reaction model in which fragments of C{sub 60}, including C{sub 2}, are considered the growth species. In particular, the nanocrystallinity of the films is most likely due to a high carbon cluster density from C{sub 60} fragmentation at or near the diamond surface, which can serve as nucleation sites for the growth of new crystallites.
Diamond nucleation and growth on mirror-polish silicon wafer pretreated by silicon ion implantation
1995-12-31
Diamond films have been obtained by hot-filament chemical vapor deposition (HF-CVD) method on silicon wafer. The substrates were pre-implantated by silicon ion beam (the ion energy is 25keV, implantation dosage is 5x10{sup 15}, 5x10{sup 16} and 2x10{sup 17}Si{sup +}/cm{sup 2}). X-ray diffraction (XRD), scanning electron microscopy (SEM), Cross-sectional transmission electron microscopy (TEM), and Raman spectroscopy were used to characterize the structure of the synthesized films.
Picosecond photoconductivity of natural and CVD diamonds
1995-12-31
Photoexcitation and recombination of nonequilibrium charge carriers in both natural gemstone diamonds and CVD (chemical vapor deposition) polycrystalline diamond films in UV spectrum region have been investigated. Transient picosecond photoconductivity technique applied permitted to conduct measurements with the time resolution better than 200 picoseconds and to register a charge carrier concentration value as low as 10{sup 12} - 10{sup 13} cm{sup -3}. The dependencies of photocurrent amplitude as a function of incident laser radiation intensity in the range from 10{sup 3} to 10{sup 10} W/cm{sup 2} have been obtained. Charge carrier lifetimes had been measured and charge carrier drift mobility were estimated. It is shown that the electronic properties of high quality thick CVD diamond films are comparable to those of the most perfect natural type IIa crystals. Investigation of Raman and luminescence spectra of diamonds have been performed along with scanning electron microscopy studies to characterise bulk and surface structure of tested specimens.
The separation of thin single crystal films from bulk diamond by MeV implantation
1994-12-31
A method has been developed by which thin (1 {mu}m) plates can be lifted off a single crystal diamond. This technique involves implanting a diamond with high energy (4-5 MeV) ions (usually carbon or oxygen) in order to create a buried amorphous layer at a depth of 1-2 {mu}m. The buried amorphous region preferentially reacts with oxygen under the right conditions, resulting in a gaseous residue. By controlling this reaction, the amorphous layer can be etched away without affecting the still crystalline surface plate. In addition to the obvious uses of thin diamond windows, these lift-off plates can also be used as substrates for homoepitaxial growth by chemical vapor deposition. Free standing homoepitaxial diamond films, between 10-20 {mu}m thick, have been produced with this method.
1993-02-15
Schottky diodes utilized for mechanical stress effect studies were fabricated using aluminum contacts to polycrystalline diamond thin films grown by a hot-filament-assisted chemical vapor deposition process. Compressive stress was found to have a large effect on the forward biased current-voltage characteristics of the diode, whereas the effect on the reverse biased characteristics was relatively small. This stress effect on the forward biased diamond Schottky diode was attributed to piezojunction and piezoresistance effects that dominated the diode current-voltage characteristics in the small and large bias regions, respectively. At a large constant forward bias current, a good linear relationship between output voltage and applied force was observed for force of less than 10 N, as predicted by the piezoresistance effect. The measured force sensitivity of the diode was as high as 0.75 V/N at 1 mA forward bias. Compared to either silicon or germanium junction diodes and tunnel diodes, polycrystalline diamond Schottky diodes not only are very stress sensitive but also have good linearity. This study shows polycrystalline diamond Schottky diodes have potential as mechanical sensors.
Texture development in diamond films grown by hot filament CVD (chemical vapor deposition) processes
1990-01-01
Diamond films with {l angle}110{r angle} and {l angle}100{r angle} textures were analyzed by x-ray diffraction, transmission electron microscopy and scanning electron microscopic examinations of the evolving growth surface topography. Results support the hypothesis that twinning can play an important role in the nucleation and growth of the {l angle}110{r angle} texture. A model similar to that proposed to explain the development of the {l angle}110{r angle} texture in silicon film growth can also explain the development of the {l angle}110{r angle} textures in diamond films. A special near {l angle}100{r angle}'' textured film with {l brace}100{r brace} facets perpendicular to the growth direction is described. This material is free of intra-crystalline stacking faults and twins. Growth mechanisms and texture development are discussed, and it is shown that randomly oriented nuclei grow into films with crystallites oriented so that the fastest growing'' crystallographic direction is normal to the substrate. 11 refs., 5 figs.
2010-01-01
We report the growth and properties of highly c-axis oriented ZnO films, by radio-frequency magnetron sputtering, on the growth side of freestanding chemical vapor deposited diamond film-substrate. Low-temperature ZnO buffer layer is required for the formation of continuous ZnO films. The morphology, structure, and optical properties of the ZnO films deposited are strongly dependent on the thickness of the buffer layer. The optimized thickness of ZnO buffer layer is about 10nm to realize high-quality ZnO films having small compressive stress and high intensity ultraviolet emission. The ZnO/diamond (growth side) system is available for the applications in numerous fields, especially for high performance surface acoustic wave devices.
Tribological study of boron nitride films
2010-01-01
Boron nitride (BN) films with different cubic and hexagonal phase compositions were deposited on silicon substrates via diamond interlayers by magnetron sputtering and electron cyclotron resonance microwave plasma chemical vapor deposition. The tribological behaviors of the BN films were investigated systematically using a ball-on-disc tribometer with silicon nitride as the counterpart. Comparison studies were also performed on sintered cubic and hexagonal BN compacts. The influence of phase compositions and surface roughness of BN coatings on their tribological characteristics was studied. The cubic BN (cBN) films showed excellent wear resistance against silicon nitride. The wear rate of the cBN films was estimated to be about 1.0x10^-^7mm^3/Nm by measuring the cross-sectional area of the...
Antibacterial activity of DLC films containing TiO2 nanoparticles
2009-01-01
Diamond-like carbon (DLC) films have been the focus of extensive research in recent years due to their potential applications as surface coatings on biomedical devices. Titanium dioxide (TiO2) in the anatase crystalline form is a strong bactericidal agent when exposed to near-UV light. In this work we investigate the bactericidal activity of DLC films containing TiO2 nanoparticles. The films were grown on 316L stainless-steel substrates from a dispersion of TiO2 in hexane using plasma-enhanced chemical vapor deposition. The composition, bonding structure, surface energy, stress, and surface roughness of these films were also evaluated. The antibacterial tests were performed against Escherichia coli (E. coli) and the results were compared to the bacterial adhesion force to the studied surfa...
2010-07-01
This review focuses on a status report on the science and technology of ultrananocrystalline diamond (UNCD) films developed and patented at Argonne National Laboratory. The UNCD material has been developed in thin film form and exhibit multifunctionalities applicable to a broad range of macro to nanoscale multifunctional devices. UNCD thin films are grown by microwave plasma chemical vapor deposition (MPCVD) or hot filament chemical vapor deposition (HFCVD) using new patented Ar-rich/CH4 or H2/CH4 plasma chemistries. UNCD films exhibit a unique nanostructure with 2-5 nm grain size (thus the trade name UNCD) and grain boundaries of 0.4-0.6 nm for plain films, and grain sizes of 7-10 nm and grain boundaries of 2-4 nm when grown with nitrogen introduced in the Ar-rich/CH4 chemistry, to produce UNCD films incorporated with nitrogen, which exhibit electrical conductivity up to semi-metallic level. This review provides a status report on the synthesis of UNCD films via MPCVD and integration with dissimilar materials like oxides for piezoactuated MEMS/NEMS, metal films for contacts, and biological matter for a new generation of biomedical devices and biosensors. A broad range of applications from macro to nanoscale multifunctional devices is reviewed, such as coatings for mechanical pumps seals, field-emission cold cathodes, RF MEMS/NEMS resonators and switches for wireless communications and radar systems, NEMS devices, biomedical devices, biosensors, and UNCD as a platform for developmental biology, involving biological cells growth on the surface. Comparisons with nanocrystalline diamond films and technology are made when appropriate.
Tribological performance of diamond and diamondlike carbon films at elevated temperatures
1995-09-01
In this study, we investigated the tribological performance of diamond and diamondlike carbon (DLC) films as a function of ambient temperature. Both films were deposited on silicon carbide (SiC) by microwave plasma chemical vapor deposition and ion-beam deposition processes. Tribological tests were performed on a reciprocating wear machine in open air (20 to 30% relative humidity) and under a 10-N load using SiC pins. For the test conditions explored, the steady- state friction coefficients of test pairs without a diamond or DLC film were 0.7 to 0.9 and the average wear rates of pins were 10{sup {minus}5} to 10{sup {minus}7} mm{sup 3}/N.m, depending on ambient temperature. DLC films reduced the steady-state friction coefficients of test pairs by factors of 3 to 5 and the wear rates of pins by two to three orders of magnitude. Low friction coefficients were also obtained with the diamond films, but wear rates of the counterface pins were high due to the very abrasive nature of these films. The wear of SiC disks coated with either diamond or DLC films was virtually unmeasurable while the wear of uncoated disks was substantial. Test results showed that the DLC films could afford low friction up to about 300{degrees}C. At higher temperatures, the DLC films became graphitized and were removed from the surface. The diamond films could withstand much higher temperatures, but their tribological behavior degraded. Raman spectroscopy and scanning electron microscopy were used to elucidate the friction and wear mechanisms of both films at high temperatures.
Tribological performance of diamond and diamondlike carbon films at elevated temperatures
In this study, we investigated the tribological performance of diamond and diamondlike carbon (DLC) films as a function of ambient temperature. Both films were deposited on silicon carbide (SiC) by microwave plasma chemical vapor deposition and ion-beam deposition processes. Tribological tests were performed on a reciprocating wear machine in open air (20 to 30% relative humidity) and under a 10-N load using SiC pins. For the test conditions explored, the steady- state friction coefficients of test pairs without a diamond or DLC film were 0.7 to 0.9 and the average wear rates of pins were 10{sup {minus}5} to 10{sup {minus}7} mm{sup 3}/N.m, depending on ambient temperature. DLC films reduced the steady-state friction coefficients of test pairs by factors of 3 to 5 and the wear rates of pins by two to three orders of magnitude. Low friction coefficients were also obtained with the diamond films, but wear rates of the counterface pins were high due to the very abrasive nature of these films. The wear of SiC disks coated with either diamond or DLC films was virtually unmeasurable while the wear of uncoated disks was substantial. Test results showed that the DLC films could afford low friction up to about 300{degrees}C. At higher temperatures, the DLC films became graphitized and were removed from the surface. The diamond films could withstand much higher temperatures, but their tribological behavior degraded. Raman spectroscopy and scanning electron microscopy were used to elucidate the friction and wear mechanisms of both films at high temperatures.
2000-01-17
Silicon is currently the most commonly used material for the fabrication of microelectromechanical systems (MEMS). However, silicon-based MEMS will not be suitable for long-endurance devices involving components rotating at high speed, where friction and wear need to be minimized, components such as 2-D cantilevers that may be subjected to very large flexural displacements, where stiction is a problem, or components that will be exposed to corrosive environments. The mechanical, thermal, chemical, and tribological properties of diamond make it an ideal material for the fabrication of long-endurance MEMS components. Cost-effective fabrication of these components could in principle be achieved by coating Si with diamond films and using conventional lithographic patterning methods in conjunction with e. g. sacrificial Ti or SiO{sub 2} layers. However, diamond coatings grown by conventional chemical vapor deposition (CVD) methods exhibit a coarse-grained structure that prevents high-resolution patterning, or a fine-grained microstructure with a significant amount of intergranular non-diamond carbon. The authors demonstrate here the fabrication of 2-D and 3-D phase-pure ultrananocrystalline diamond (UNCD) MEMS components by coating Si with UNCD films, coupled with lithographic patterning methods involving sacrificial release layers. UNCD films are grown by microwave plasma CVD using C{sub 60}-Ar or CH{sub 4}-Ar gas mixtures, which result in films that have 3--5 nm grain size, are 10--20 times smoother than conventionally grown diamond films, are extremely resistant to corrosive environments, and are predicted to have a brittle fracture strength similar to that of single crystal diamond.
1995-12-31
Distinctive frequency dependent capacitance-voltage (C-V) characteristics of boron-doped chemical vapor deposited (CVD) diamond thin film Schottky diodes were observed. The results exhibited not only small signal differential capacitance dependence on both the reverse bias voltage and test frequency, but also linear inverse squared capacitance-voltage characteristics at all test frequencies, ranging from 1 kHz to 1 MKz. The Schottky barrier heights of both Al- and Au-hot filament CVD diamond Schottky diodes were determined to be 1.04 and 1.09 eV, respectively. An effective carrier concentration in the range of 0.5 to 1.5 x 10{sup 17}cm {sup {minus}3} was estimated. The distinct C-V characteristics obtained in this study are attributed to careful surface cleaning and the use of moderate boron doped diamond thin films.
(Chemically vapor deposited diamond films)
1990-09-22
The NATO-ASI on Diamond and Diamond-Like Films and Coatings'' was an opportunity for us to learn the latest research results from ongoing programs in the leading laboratories of the world and relate them to our work. Specific examples are given in the comprehensive report which follows. The meeting format provided an ideal environment to meet and interact with our international counterparts. It is clear that our studies are well regarded, and that we have established an excellent reputation in a short time. New opportunities for collaboration were identified. A panel discussion at the end of the meeting addressed the needs and opportunities in the synthesis of CVD diamond. The key scientific needs are those related to modeling the nucleation and growth processes and to elucidation of the critical roles of atomic hydrogen and the mechanisms of carbon addition to the growing surfaces. The development and more extensive use of in situ diagnostics for both surface and gas phases are important to solving these issues. The more immediate practical questions concern the identification of the growth-rate-limiting steps, the relation of growth parameters to the resulting film structure, and the dependence of properties on structure.
In vivo preliminary evaluation of bone-microcrystalline and bone-nanocrystalline diamond interfaces
2010-01-01
Chemical vapor deposited diamond is a new potential biomedical material which has the advantage of chemical inertness, extreme hardness and low coefficient of friction, among others. In orthopedics and maxillofacial surgery, these properties could improve implant performance, reducing metallic corrosion, particle wear, inflammatory reactions and bone loss. In the present study, two types of chemical vapor deposition (CVD) diamonds have been analyzed: microcrystalline diamonds (MD) and nanocrystalline diamonds (ND), both produced by hot-filament chemical vapor deposition. The diamond tubes were previously characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and Raman scattering spectroscopy (RSS). The aim of this study was to verify the interface between bone a...
2010-01-01
Synthesis of diamond-like carbon (DLC) films with UV-induced-hydrophilicity function was studied by inductively-coupled plasma (ICP) chemical vapor deposition. Titanium tetraisopropoxide (TTIP) and oxygen gases were employed as the precursors to deposit diamond-like nanocomposite films containing titanium dioxide (TiO2) nanoparticles. X-ray diffraction and high-resolution transmission electron microscopy revealed that TiO2 nanocrystallites were formed in the DLC films when oxygen concentration was higher than TTIP concentration during deposition. The DLC nanocomposite film was hydrophobic without ultraviolet (UV) irradiation, and became highly hydrophilic under UV irradiation, exhibiting the self-cleaning effect. A very broad peak centered at 1580cm^-^1 was observed in the Raman spectra co...
2007-01-01
Diamond like carbon thin films with Cu impurity were made from acetylene by RF plasma chemical vapor deposition method on silicon and glass substrates with different deposition pressures. In this work we study the annealing effect on the properties of the Cu-Diamond like carbon films. Films were annealed in Ar atmosphere at different temperatures (200degC, 300degC, and 400degC) for 30 min. Rutherford backscattering spectroscopy and XRD spectra and atomic force microscopy from the made films were used to study the carbon surface density, the carbon /copper atomic ratio ,thickness, Cu nano structure and surface roughness. Collected information reveals that increasing in annealing temperature decreases thickness, electrical resistivity and surface roughness and from other hand increases Cu ...
Tribological properties of undoped and boron-doped nanocrystalline diamond films
2008-11-28
Undoped and boron-doped nanocrystalline (NCD) diamond films were deposited on mirror polished Ti-6Al-4V substrates in a Microwave Plasma Assisted Chemical Vapor Deposition system. Sliding wear tests were conducted in ambient air with a nanotribometer. A systematic study of the tribological properties for both undoped and boron-doped NCD films were carried out. It was found for diamond/diamond sliding, coefficient of friction decreases with increasing normal loads. It was also found that the wear rate of boron-doped NCD films is about 10 times higher than that of undoped films. A wear rate of {approx} 5.2 x 10{sup -9} mm{sup 3}/Nm was found for undoped NCD films. This value is comparable to the best known value of that of polished polycrystalline diamond films. Although no surface deformation, film delamination or micro-cracking were observed for undoped films, boron-doped NCD film undergoes a critical failure at a normal stress of 2.2 GPa, above which surface deformation is evident. Combined with high hardness and modulus, tunable conductivity and improved open air thermal stability, boron-doped nanocrystalline diamond film has tremendous potentials for applications such as Atomic Force Microscope probes, Micro-Electro-Mechanical System devices and biomedical sensors.
Diamond and diamond-like carbon films for advanced electronic applications
Aim of this laboratory-directed research and development (LDRD) project was to develop diamond and/or diamond-like carbon (DLC) films for electronic applications. Quality of diamond and DLC films grown by chemical vapor deposition (CVD) is not adequate for electronic applications. Nucleation of diamond grains during growth typically results in coarse films that must be very thick in order to be physically continuous. DLC films grown by CVD are heavily hydrogenated and are stable to temperatures {le} 400{degrees}C. However, diamond and DLC`s exceptional electronic properties make them candidates for integration into a variety of microelectronic structures. This work studied new techniques for the growth of both materials. Template layers have been developed for the growth of CVD diamond films resulting in a significantly higher nucleation density on unscratched or unprepared Si surfaces. Hydrogen-free DLC with temperature stability {le} 800{degrees}C has been developed using energetic growth methods such as high-energy pulsed-laser deposition. Applications with the largest system impact include electron-emitting materials for flat-panel displays, dielectrics for interconnects, diffusion barriers, encapsulants, and nonvolatile memories, and tribological coatings that reduce wear and friction in integrated micro-electro-mechanical devices.
Diamond and diamond-like carbon films for advanced electronic applications
1996-03-01
Aim of this laboratory-directed research and development (LDRD) project was to develop diamond and/or diamond-like carbon (DLC) films for electronic applications. Quality of diamond and DLC films grown by chemical vapor deposition (CVD) is not adequate for electronic applications. Nucleation of diamond grains during growth typically results in coarse films that must be very thick in order to be physically continuous. DLC films grown by CVD are heavily hydrogenated and are stable to temperatures {le} 400{degrees}C. However, diamond and DLC`s exceptional electronic properties make them candidates for integration into a variety of microelectronic structures. This work studied new techniques for the growth of both materials. Template layers have been developed for the growth of CVD diamond films resulting in a significantly higher nucleation density on unscratched or unprepared Si surfaces. Hydrogen-free DLC with temperature stability {le} 800{degrees}C has been developed using energetic growth methods such as high-energy pulsed-laser deposition. Applications with the largest system impact include electron-emitting materials for flat-panel displays, dielectrics for interconnects, diffusion barriers, encapsulants, and nonvolatile memories, and tribological coatings that reduce wear and friction in integrated micro-electro-mechanical devices.
Aerosol-Assisted Chemical Vapor Deposited Thin Films for Space Photovoltaics
Copper indium disulfide thin films were deposited via aerosol-assisted chemical vapor deposition using single source precursors. Processing and post-processing parameters were varied in order to modify morphology, ...
Tribological behavior of diamond-like carbon film with different tribo-pairs: A size effect study
2008-08-30
A friction force microscope (FFM) with different probes and a ball-on-disk (BOD) tribo-meter were used to investigate the tribological properties of diamond-like carbon (DLC) films. DLC films were prepared by chemical vapor deposition (CVD) method by altering the deposition parameters, and their morphologies and structural information were examined with an atomic force microscope (AFM) and the Raman spectrum. The wear traces of the DLC films after frictional tests were analyzed by an optical microscope. It is found that surface roughness and adhesion play important roles in characterizing the tribological properties of DLC films using FFM. Moreover, the debris accumulation is another significant factor affecting the frictional behavior of DLC films, especially for the sharp tip. The difference in coefficients of friction (COFs) obtained by the BOD method among different DLC films under water lubrication is much smaller than the case without water lubrication. The variation trends in COF for the flat tip and the BOD test are similar in comparison with the result obtained with the sharp tip. The wear traces after frictional tests suggest that DLC films under water lubrication are prone to be damaged more readily.
Atomic oxygen resistant behaviors of Mo/diamond-like carbon nanocomposite lubricating films
2009-01-15
Mo doped diamond-like carbon (Mo/DLC) films were deposited on Si substrates via unbalanced magnetron sputtering of molybdenum combined with plasma chemical vapor deposition of CH{sub 4}/Ar. The microstructure of the films, characterized by transmission electron microscopy and selected area electron diffraction, was considered as a nanocomposite with nano-sized MoC particles uniformly embedded in the amorphous carbon matrix. The structure, morphology, surface composition and tribological properties of the Mo/DLC films before and after the atomic oxygen (AO) irradiation were investigated and a comparison made with the DLC films. The Mo/DLC films exhibited more excellent degradation resistant behaviors in AO environment than the DLC films, and the MoC nanoparticles were proved to play a critical role of preventing the incursion of AO and maintaining the intrinsic structure and excellent tribological properties of DLC films.
Oxygen-terminated nanocrystalline diamond film as an efficient anode in photovoltaics
2010-04-23
The potential of using p-doped nanocrystalline diamond as the anode for organic solar cells, because of its outstanding photostability and well-matched energetics with organic dyes, is demonstrated. The interface dipole and open-circuit potential can be tuned by varying the surface termination on diamond. Oxygenated nanocrystalline diamond (O-NCD) exhibits the best photocurrent conversion among all the surface-treated electrodes studied in this work because of its large open-circuit potential. The good energy alignment of the valence band of O-NCD with the HOMO of poly(3-hexylthiophene), as well as its p-doped characteristics, suggest that O-NCD can replace the hole transport layer, such as PEDOT:PSS, needed for efficient performance on indium tin oxide (ITO) electrodes. If the sheet resistance and optical transparency on NCD can be further optimized, chemical-vapor-deposited diamond electrodes may offer a viable alternative to ITO and fluorinated tin oxide (FTO). (Abstract Copyright [2010], Wiley Periodicals, Inc.)
Bonding regeneration: The driving force of heteroepitaxy diamond grain coalescence on (001) silicon
1998-12-31
The grain coalescence phenomenon in the growth of heteroepitaxial diamond film on (001) silicon substrate by microwave plasma chemical vapor deposition was examined by using high-resolution electron microscopy. It was shown that this phenomenon evidently occurs between two diamond grains with a small-angle tilt. The coalescence was completed after some more growth steps following the meeting of such two grains, indicating the difficulty for the lattice matching in grain boundary. By performing simulation of a step-by-step growth of two diamond grains on a (001) silicon substrate with molecular orbital PM3 method, it was shown that the bonding regeneration between the two grains is essential for the coalescence and the coalescence is only possible when the orientation difference between the grains is sufficiently small so as to allow efficient overlap of electron cloud in the grain boundary. This study indicates that single crystal diamond growth may be possible by the current CVD growth techniques via further reduction of the surface roughness to gain a heteroepitaxy with very small grain tilting.
Selective detection of phosgene by nanocrystalline diamond layer
2009-01-01
Nanocrystalline diamond (NCD) films were grown on gold/Al2O3 substrate using microwave plasma-enhanced chemical vapor deposition (PECVD) process. The NCD morphology was controlled by the deposition time and it was investigated by scanning electron microscopy (SEM). Gas sensing properties of NCD surface conductivity to humid air, CO2, NH3, and COCl2 gases were measured by impedance measurements at room and at high temperature (140 degreeC). The H-terminated NCD surface shows a significant response to oxidizing gas (humid air, COCl2) in comparison to reducing gases (CO2, NH3).
Polycrystalline diamond based detector for Z-pinch plasma diagnosis
A detector setup based on polycrystalline chemical-vapor-deposition diamond film is developed with great characteristics: low dark current (lower than 60 pA within 3 V/?m), fast pulsed response time (rise time: 2-3 ns), flat spectral response (3-5 keV), easy acquisition, low cost, and relative large sensitive area. The characterizing data on Qiangguang-I accelerator show that this detector can satisfy the practical requirements in Z-pinch plasma diagnosis very well, which offers a promising prototype for the x-ray detection in Z-pinch diagnosis.
Optical properties of boron-doped diamond
2005-08-23
We report optical reflectivity study on pure and boron-doped diamond films grown by a hot-filament chemical vapor deposition method. The study reveals the formation of an impurity band close to the top of the valence band upon boron-doping. A schematic picture for the evolution of the electronic structure with boron doping was drawn based on the experimental observation. The study also reveals that the boron doping induces local lattice distortion, which brings an infrared-forbidden phonon mode at 1330 cm$^{-1}$ activated in doped sample. The antiresonance characteristic of the mode in conductivity spectrum evidences the very strong coupling between electrons and this phonon mode.
Operating parameters of CVD diamond detectors for radiation dosimetry
2010-01-01
A prototype clinical radiation detector based on commercially available single crystal diamond film made via chemical vapor deposition was investigated to determine optimal operating parameters for clinical dosimetry. This study examined how changes in applied electric field affected dosimetric performance, and determined a preferred operating voltage within the limits of clinical dosimetry equipment. Dosimetric analysis included leakage current, response dynamics such as rise and fall times, sensitivity, polarity and dependence on dose and dose rate. The results of this study indicate a preference for using a setting of 62.5 V due to its minimal rise time of 2 s, including a faster time to equilibrium, yet sufficient sensitivity of 37 nC Gy-1, which was nearly independent of polarity. At this voltage, a wider range of dose may therefore be recorded with ...
Operating parameters of CVD diamond detectors for radiation dosimetry
2010-01-01
A prototype clinical radiation detector based on commercially available single crystal diamond film made via chemical vapor deposition was investigated to determine optimal operating parameters for clinical dosimetry. This study examined how changes in applied electric field affected dosimetric performance, and determined a preferred operating voltage within the limits of clinical dosimetry equipment. Dosimetric analysis included leakage current, response dynamics such as rise and fall times, sensitivity, polarity and dependence on dose and dose rate. The results of this study indicate a preference for using a setting of 62.5V due to its minimal rise time of 2s, including a faster time to equilibrium, yet sufficient sensitivity of 37nCGy−1, which was nearly independent of polarity....
Improvement of DLC electrochemical corrosion resistance by addiction of fluorine
2010-01-01
The combination of chemical and mechanical properties of diamond-like carbon (DLC) films opens the possibilities for its use in electrochemical applications. DLC electrochemical corrosion behavior is heavily dependent on deposition techniques and precursor gas. Fluorinated-DLC combines the superlative properties of diamond and teflon and becomes one of the most suitable coating for tribological applications. F-DLC was grown over 316L stainless steel using plasma enhanced chemical vapor deposition by varying the ratio of carbon tetrafluoride and methane. The influence of fluorine content on deposition rate, composition, bonding structure, surface energy, hardness, stress, and surface roughness was investigated. Emphasis was placed on the investigation of F-DLC electrochemical corrosion beha...
Evaluation of corrosion resistance of diamond-like carbon films deposited onto AISI 4340 steel
2010-01-01
The corrosion resistance of amorphous diamond-like carbon (DLC) coatings deposited by radio frequency plasma enhanced chemical vapor deposition (rf-PECVD) technique on AISI 4340 steel substrates was evaluated under saline (5% NaCl) and acid (1700ppm H2SO4) atmospheres. The corrosion process was investigated by surface characterization and electrochemical methods, such as potentiostatic polarization and electrochemical impedance spectroscopy (EIS). DLC coatings effectively protected the substrate after 48h in a salt fog chamber and after the first Kesternich cycle. For comparison, under the same conditions, titanium nitride (TiN) coatings did not protect the substrate even for 2h of saline exposure and even for the first Kesternich cycle. Although the DLC coatings resisted well to the...
Characterization of DC magnetron sputtered diamond-like carbon (DLC) nano coating
2008-01-01
Development in vapor deposition techniques over the last two decades has led to the introduction of many advanced coatings for metal-cutting tools. This paper examines the characteristics of multilayer Ti, TiN, and diamond-like carbon (DLC) coatings deposited on standard tool substrates at varying sputtering parameters and conditions, such as power density, partial pressure, substrate temperature, and reactive gases. The characteristics of films were examined using an X-ray diffractometer, Raman microscope, surface profilometer (to measure the thickness of the coating), Rockwell hardness tester (to test adhesion), and a micro hardness tester. The pin-on-disc test setup was used to find the coefficient of friction of the coatings. The results indicated that a graded multilayer coating showe...
High performances surface acoustic wave (SAW) filters based on aluminium nitride (AlN)/diamond layered structure have been fabricated. The C-axis oriented aluminum nitride films with various thicknesses were sputtered on unpolished nucleation side of free-standing polycrystalline chemical vapor deposition (CVD) diamond obtained by silicon substrate etching. Experimental results show that high order modes as well as Rayleigh waves are excited. Experimental results are in good agreement with the theoretical dispersion curves determined by software simulation with Green's function formalism. We demonstrate that high phase velocity first mode wave (so-called Sezawa wave) with high electromechanical coupling coefficient are obtained on AlN/diamond structure. This structure also has a low temperature coefficient of frequency (TCF), and preliminary results suggest that a zero TCF could be expected.
2008-08-01
Nanocrystalline diamond (NCD) films with a thickness of {approx}6 {micro}m and with average grain sizes ranging from 60 to 9 nm were deposited on silicon wafers using a hot-filament chemical vapor deposition (HFCVD) process. These samples were then characterized with the goal to identify correlations between grain size, chemical composition and mechanical properties. The characterization reveals that our films are phase pure and exhibit a relatively smooth surface morphology. The levels of sp{sup 2}-bonded carbon and hydrogen impurities are low, and showed a systematic variation with the grain size. The hydrogen content increases with decreasing grain size, whereas the sp{sup 2} carbon content decreases with decreasing grain size. The material is weaker than single crystalline diamond, and both stiffness and hardness decrease with decreasing grain size. These trends suggest gradual changes of the nature of the grain boundaries, from graphitic in the case of the 60 nm grain size material to hydrogen terminated sp{sup 3} carbon for the 9 nm grain size material. The films exhibit low levels of internal stress and freestanding structures with a length of several centimeters could be fabricated without noticeable bending.
A microwave plasma system for the deposition of diamond films
1996-12-31
There has been considerable interest in applying rf plasma to industrial applications such as etching, deposition, sputtering, surface cleaning, and ion implantation for thin film processing. In the effort of making rf plasma sources, the main concerns are the density and energy distribution of the electrons. These are closely related to the frequency and power of the rf source. Thus microwaves have long been considered the ideal source. In this work, a microwave plasma source is designed for the application of chemical vapor deposition of diamond films. Microwaves provided by a magnetron are fed into a cylindrical cavity through a loop antenna. The cavity can be adjusted to excite the TM{sub 011} to TM{sub 013} modes. Using a large cavity to reduce the power density, the microwave coupling into the cavity is expected to be more efficient. However, in order to use microwave power effectively, only a small portion of the cavity separated by a glass enclosure to keep the vacuum pressure is used as the reaction chamber. Thus the plasma is produced only in the reaction chamber, and the effect of the plasma loading on the microwave coupling is also minimized. The experimental results indeed show that a very stable plasma can be produced, over a large range of incident power levels. A Langmuir probe is inserted to measure the plasma characteristics. The results of probe measurements and diamond film deposits are presented.
Diamond films grown from fullerene precursors
1995-07-01
Fullerene precursors have been shown to result in the growth of diamond films from argon microwave plasmas. In contradistinction to most diamond films grown using conventional methane-hydrogen mixtures, the fullerene-generated films are nanocrystalline and smooth on the nanometer scale. They have recently been shown to have friction coefficients approaching the values of natural diamond. It is clearly important to understand the development of surface morphology during film growth from fullerene precursors and to elucidate the factors leading to surface roughness when hydrogen is present in the chemical vapor deposition (CVD) gas mixtures. To achieve these goals, we are measuring surface reflectivity of diamond films growing on silicon substrates over a wide range of plasma processing conditions. A model for the interpretation of the laser interferometric data has been developed, which allows one to determine film growth rate, rms surface roughness, and bulk losses due to scattering and absorption. The rms roughness values determined by reflectivity are in good agreement with atomic force microscope (AFM) measurements. A number of techniques, including high-resolution transmission electron microscopy (HRTEM) and near-edge x-ray absorption find structure (NEXAFS) measurements, have been used to characterize the films. A mechanism for diamond-film growth involving the C{sub 2} molecule as a growth species will be presented. The mechanism is based on (1) the observation that the optical emission spectra of the fullerene- containing plasmas are dominated by the Swan bands of C{sub 2} and (2) the ability of C{sub 2} to insert directly into C-H and C-C bonds with low activation barriers, as shown by recent theoretical calculations of reactions of C{sub 2} with carbon clusters.
Diamond films grown from fullerene precursors
Fullerene precursors have been shown to result in the growth of diamond films from argon microwave plasmas. In contradistinction to most diamond films grown using conventional methane-hydrogen mixtures, the fullerene-generated films are nanocrystalline and smooth on the nanometer scale. They have recently been shown to have friction coefficients approaching the values of natural diamond. It is clearly important to understand the development of surface morphology during film growth from fullerene precursors and to elucidate the factors leading to surface roughness when hydrogen is present in the chemical vapor deposition (CVD) gas mixtures. To achieve these goals, we are measuring surface reflectivity of diamond films growing on silicon substrates over a wide range of plasma processing conditions. A model for the interpretation of the laser interferometric data has been developed, which allows one to determine film growth rate, rms surface roughness, and bulk losses due to scattering and absorption. The rms roughness values determined by reflectivity are in good agreement with atomic force microscope (AFM) measurements. A number of techniques, including high-resolution transmission electron microscopy (HRTEM) and near-edge x-ray absorption find structure (NEXAFS) measurements, have been used to characterize the films. A mechanism for diamond-film growth involving the C{sub 2} molecule as a growth species will be presented. The mechanism is based on (1) the observation that the optical emission spectra of the fullerene- containing plasmas are dominated by the Swan bands of C{sub 2} and (2) the ability of C{sub 2} to insert directly into C-H and C-C bonds with low activation barriers, as shown by recent theoretical calculations of reactions of C{sub 2} with carbon clusters.
2007-01-01
Fluorine-doped diamond-like carbon (F-DLC) has recently drawn a great deal of attention as a more non-thrombogenic coating than conventional DLC for blood-contacting medical devices. We conducted quantitative depth profiling of F-DLC film by X-ray photoelectron spectroscopy (XPS) in order to elucidate the effects of fluorine and fluorine distribution in F-DLC film in connection with the prevention of surface blood adhesion. F-DLC films were prepared on silicon substrates using the radio frequency plasma enhanced chemical vapor deposition method, and the thickness of films was approx 50 nm. 50-nm-thick F-DLC film samples were etched at 10-nm thickness intervals using argon plasma, and each surface was examined by XPS. Thereafter, each etched film layer was incubated with platelet-rich plasma isolated from human whole blood, and the platelet-covered ...
2010-01-01
Fluorinated diamond-like carbon (F-DLC) films were deposited on polytetrafluoroethylene (PTFE) using radio frequency (RF) plasma-enhanced chemical vapor deposition (CVD) by changing the ratio of tetrafluoromethane (CF4) and methane (CH4). To enhance the adhesion strength of the F-DLC film to the PTFE substrate, the PTFE surface was modified with a N2 plasma pre-treatment. XPS analysis of the films showed that the CC bond decreased with increases in the CF4 ratio, whereas the CF bond increased with the CF4 ratio. The F/C ratio of the film also increased with the CF4 ratio. The pull-out test showed that the adhesion strengths of the films (CF4-060%) were improved with the plasma pre-treatment. In the film without the plasma pre-treatment, adhesion strength increased with the CF4 rat...
1997-07-01
Selected area deposition of diamond films on silicon substrates was successfully achieved using the patterned Pt layer as a nucleation inhibitor in the chemical vapor deposition process. The planar diamond film array thus made possesses good electron field emission properties, that is, emission current density of (J{sub e}){sub Si}=150{mu}A/cm{sup 2} (under 23.6 V/{mu}m) and turn on field of (E{sub o}){sub Si}=10V/{mu}m. Precoating a thin Au layer (20 nm) on a Si surface further increased the emission current density to (J{sub e}){sub Au/Si}=960{mu}A/cm{sup 2} (under 23.6 V/{mu}m) with (E{sub o}){sub Au/Si}=10V/{mu}m. The effective work functions ({phi}) estimated by Fowler{endash}Nordheim plots of the I{endash}V characteristics are ({phi}){sub Si}=0.059eV and ({phi}){sub Au/Si}=0.085eV. The emission properties of both planar diamond film arrays satisfy the requirement for applying as the electron emitters in the flat panel displays. {copyright} {ital 1997 American Institute of Physics.}
Method of plasma enhanced chemical vapor deposition of diamond using methanol-based solutions
Briefly described, methods of forming diamond are described. A representative method, among others, includes: providing a substrate in a reaction chamber in a non-magnetic-field microwave plasma system; introducing, ...
Electron Emission Observations from As-Grown and Vacuum-Coated Chemical Vapor Deposited Diamond
Field emission has been observed from chemical vapor deposited diamond grown on Mo and Si substrates. Emission was observed at fields as low as 20 kV/cm. The samples were tested in the as-grown form, and after ...
1994-05-01
New thin film semiconductors such as silicon, silicon carbide and diamond can be fabricated using the CVD (Chemical Vapor Deposition) technique. Their structural and electrical characteristics are presented. Also, their potential use as nuclear detectors is investigated. The thin film based technology allows the fabrication of multilayer detectors inter-coupled with scintillators or converters. According to the original concept of ``Smart Modular Detector Systems``, developed at DEIN, multilayer detectors can be specifically tailored to fit most of the requirements encountered with nuclear measurements: special geometry, type of particle to be detected, etc. Finally, present Research and Development projects in progress at DEIN are presented along with some preliminary results. (authors). 4 tabs., 12 figs., 13 refs.
Deposition Of Materials Using A Simple Planar Coil Radio Frequency Inductively Coupled Plasma System
2009-01-01
A planar coil RF inductively coupled plasma (PC-RFICP) systems is set up for the purpose of thin film deposition. The system is powered by a 13.56 MHz, 550 W, 50 OMEGA RF generator. The RF power is transferred to the plasma via a planar induction coil. The impedance matching unit consists of an air core step-down transformer and a tunable vacuum capacitor. This system is used for the plasma enhanced chemical vapor deposition (PECVD) of diamond-like carbon (DLC) film on silicon substrate, and hydrogenated amorphous carbon (a-C:H) film
Analysis of the surface structure of HFCVD diamond films
1995-07-01
Structure analysis was carried out on various surface features of diamond films using scanning electron microscopy (SEM) and atomic force microscopy (AFM). The films were grown via hot filament assisted chemical vapor deposition (HFCVD) in methane and hydrogen gas mixtures. The authors investigated the surfaces of films grown under parameters selected to produce certain textures or surface features such as penetration twins or hopper shaped faces. The SEM images of these films show that the {l_brace}100{r_brace} planes are usually flatter than the {l_brace}111{r_brace}. The {l_brace}111{r_brace} planes show interesting growth features. The ``hopper`` shaped structures were imaged in the tapping mode of the AFM, and the angles between planes and their orientations have been determined. These AFM and SEM images are presented with quantitative analyses of the exposed surfaces. Detailed quantitative information will be useful in understanding the growth of these films.
1997-11-01
Nanocrystalline diamond films have been synthesized by microwave plasma enhanced chemical vapor deposition using N{sub 2}/CH{sub 4} as the reactant gas without additional H{sub 2}. The nanocrystalline diamond phase has been identified by x-ray diffraction and transmission electron microscopy analyses. High resolution secondary ion mass spectroscopy has been employed to measure incorporated nitrogen concentrations up to 8{times}10{sup 20}atoms/cm{sup 3}. Electron field emission measurements give an onset field as low as 3.2V/{mu}m. The effect of the incorporated nitrogen on the field emission characteristics of the nanocrystalline films is discussed. {copyright} {ital 1997 American Institute of Physics.}
2010-01-01
Crystallinity of freestanding large (size: ~9x9mm) undoped single crystal (SC) diamond films grown by plasma chemical vapor deposition (CVD) was investigated using optical transmission spectroscopy, polarized optical microscope, X-ray rocking curves, X-ray topographs and photoluminescence. The production of the freestanding film was performed by elimination of the substrates using a so-called ''lift-off method'' after the growth of a homoepitaxial thick-film on a pre-ion-implanted substrate. The remarkable optical absorption in the wavelength from ultraviolet to near-infrared region (220-2500nm) was not seen, similarly to a high-pressure, high-temperature (HPHT) synthetic type-IIa diamond. The cross-nicol optical microscope image demonstrated that there are patchy white regions and many do...
Morphology and electron emission properties of nanocrystalline CVD diamond thin films.
1998-01-30
Nanocrystalline diamond thin films have been produced by microwave plasma-enhanced chemical vapor deposition (MPECVD) using C{sub 60}/Ar/H{sub 2} or CH{sub 4}/Ar/H{sub 2} plasmas. Films grown with H{sub 2} concentration {le} 20% are nanocrystalline, with atomically abrupt grain boundaries and without observable graphitic or amorphous carbon phases. The growth and morphology of these films are controlled via a high nucleation rate resulting from low hydrogen concentration in the plasma. Initial growth is in the form of diamond, which is the thermodynamic equilibrium phase for grains {le}5 nm in diameter. Once formed, the diamond phase persists for grains up to at least 15-20 nm in diameter. The renucleation rate in the near-absence of atomic hydrogen is very high ({approximately} 10{sup 10} cm{sup {minus}2} sec{sup {minus}1}), limiting the average grain size to a nearly constant value as the film thickness increases, although the average grain size increases as hydrogen is added to the plasma. For hydrogen concentrations less than {approximately}20%, the growth species is believed to be the carbon dimer, C{sub 2}, rather than the CH{sub 3}* growth species associated with diamond film growth at higher hydrogen concentrations. For very thin films grown from the C{sub 60} precursor, the threshold field (2 to {approximately}60 volts/micron) for cold cathode electron emission depends on the electrical conductivity and on the surface topography, which in turn depends on the hydrogen concentration in the plasma. A model of electron emission, based on quantum well effects at the grain boundaries is presented. This model predicts promotion of the electrons at the grain boundary to the conduction band of diamond for a grain boundary width {approximately} 3--4 {angstrom}, a value within the range observed by TEM.
Etching Effects During the Chemical Vapor Deposition of (100) Diamond
1999-08-02
Current theories of CVD growth on (100) diamond are unable to account for the numerous experimental observations of slow-growing, locally smooth (100)(2x1) films. In this paper they use quantum mechanical calculations of diamond surface thermochemistry and atomic-scale kinetic Monte Carlo simulations of deposition to investigate the efficacy of preferential etching as a mechanism that can help to reconcile this discrepancy. This etching mechanism allows for the removal of undercoordinated carbon atoms from the diamond surface. In the absence of etching, simulated growth on the (100)(2x1) surface is faster than growth on the (110) and (111) surfaces, and the (100) surface is atomically rough. When etching is included in the simulations, the (100) growth rates decrease to values near those observed experimentally, while the rates of growth on the other surfaces remain largely unaffected and similar to those observed experimentally. In addition, the etching mechanism promotes the growth of smooth (100) surface regions in agreement with numerous scanning probe studies.
2007-01-01
Silicon-incorporated diamond-like carbon (Si-DLC) films were deposited via dc plasma-enhanced chemical vapor deposition (PECVD), on glass and alumina substrates at a substrate temperature 300 deg. C. The precursor gas used was acetylene and for Si incorporation, tetraethyl orthosilicate dissolved in methanol was used. Si atomic percentage in the films was varied from 0% to 19.3% as measured from energy-dispersive X-ray analysis (EDX). The binding energies of C 1s, Si 2s and Si 2p were determined from X-ray photoelectron spectroscopic studies. We have observed low-macroscopic field electron emission from Si-DLC thin films deposited on glass substrates. The emission properties have been studied for a fixed anode-sample separation of 80 mum for different Si atomic percentages in the films. The turn-on field was also found to vary from 16.19 to 3.61 ...
2010-01-01
A 30kW-powered DC Arcjet Plasma enhanced chemical-vapor deposition (CVD) system was applied to grow diamonds which included the nano-crystal free-standing film, the nano-/micro-crystal layered free-standing film, the gradient micro-crystal free-standing film and the millimeter-sized grain. The free-standing film quality, such as the roughness, the sp^2 content, the residual stress and the grain morphology, was studied by an atomic force microscope (AFM), Raman spectra, a scanning electron microscope (SEM) and a high resolution electron microscope (HREM). In large-sized grain deposition, as-grown deposit was obtained about 1x1x1mm^3 in size under the condition of 10mm/h of the substrate moving speed without Nitrogen enhancement. Characterized by Raman spectra and Laue back reflection X-ray ...
Diamond film formation using RF plasma CVD assisted by water vapor enhanced hydrogen radical source
1995-12-31
For the formation of diamond thin films, CH{sub 3} and H radicals have been regarded as the important reactive species. In order to realize thin films of high quality by using plasma enhanced chemical vapor deposition (CVD) method, it is desirable to supply selectively reactive species suitable for the film formation onto the substrate. In this work, the authors report on the development of a unique plasma CVD method, plasma CVD assisted by remote radical source, which is a novel technique to control plasma by changing densities of specific radicals while keeping the electron temperature and electron density almost constant in the plasma. This system consists of three parts, a magnetoactive parallel plate RF plasma reactor, a compact microwave discharge region for a source of H radicals, and a CO{sub 2} laser for the substrate heating. By using this system diamond thin film was successfully synthesized. In addition, the effect of H{sub 2}O addition to the microwave H{sub 2} plasma as the H radical source on the diamond film formation was investigated. It was found that the addition of an appropriate amount of H{sub 2}O to the microwave H{sub 2} plasma enhanced etching of non-diamond phase and selective growth of diamond in the RF plasma at relatively low substrate temperature below 500 C.
Tribological properties of nanocrystalline diamond films
In this paper, the authors present the friction and wear properties of nanocrystalline diamond (NCD) films grown in A-fullerene (C{sub 60}) and Ar-CH{sub 4} microwave plasmas. Specifically, they address the fundamental tribological issues posed by these films during sliding against Si{sub 3}N{sub 4} counterfaces in ambient air and inert gases. Grain sizes of the films grown by the new method are very small (10--30 nm) and are much smoother (20-40 nm, root mean square) than those of films grown by the conventional H{sub 2}-CH{sub 4} microwave-assisted chemical-vapor-deposition (CVD) process. Transmission electron microscopy (TEM) revealed that the grain boundaries of these films are very sharp and free of nondiamond phases. The microcrystalline diamond (MCD) films grown by most conventional methods consist of large grains and a rough surface finish, which can cause severe abrasion during sliding against other materials. The friction coefficients of films grown by the new method (i.e., in Ar-C{sub 60} and Ar-CH{sub 4} plasmas) are comparable to those of natural diamond, and wear damage on counterface materials is minimal. Fundamental tribological studies indicate that these films may undergo phase transformation during long-duration, high-speed and/or high-load sliding tests and that the transformation products trapped at the sliding interfaces can intermittently dominate friction and wear performance. Using results from a combination of TEM, electron diffraction, Raman spectroscopy, and electron energy loss spectroscopy (EELS), they describe the structural chemistry of the debris particles trapped at the sliding interfaces and elucidate their possible effects on friction and wear of NCD films in dry N{sub 2}. Finally, they suggest a few potential applications in which NCD films can improve performance and service lives.
Tribological properties of nanocrystalline diamond films
2000-01-26
In this paper, the authors present the friction and wear properties of nanocrystalline diamond (NCD) films grown in A-fullerene (C{sub 60}) and Ar-CH{sub 4} microwave plasmas. Specifically, they address the fundamental tribological issues posed by these films during sliding against Si{sub 3}N{sub 4} counterfaces in ambient air and inert gases. Grain sizes of the films grown by the new method are very small (10--30 nm) and are much smoother (20-40 nm, root mean square) than those of films grown by the conventional H{sub 2}-CH{sub 4} microwave-assisted chemical-vapor-deposition (CVD) process. Transmission electron microscopy (TEM) revealed that the grain boundaries of these films are very sharp and free of nondiamond phases. The microcrystalline diamond (MCD) films grown by most conventional methods consist of large grains and a rough surface finish, which can cause severe abrasion during sliding against other materials. The friction coefficients of films grown by the new method (i.e., in Ar-C{sub 60} and Ar-CH{sub 4} plasmas) are comparable to those of natural diamond, and wear damage on counterface materials is minimal. Fundamental tribological studies indicate that these films may undergo phase transformation during long-duration, high-speed and/or high-load sliding tests and that the transformation products trapped at the sliding interfaces can intermittently dominate friction and wear performance. Using results from a combination of TEM, electron diffraction, Raman spectroscopy, and electron energy loss spectroscopy (EELS), they describe the structural chemistry of the debris particles trapped at the sliding interfaces and elucidate their possible effects on friction and wear of NCD films in dry N{sub 2}. Finally, they suggest a few potential applications in which NCD films can improve performance and service lives.
Thermoluminescence assessment of 0.5, 1.0 and 4.0 m thick HFCVD undoped diamond films
2009-01-01
Chemical vapor deposition (CVD) diamond has not found extensive application as a thermoluminescence (TL) dosimeter, mainly because its TL glow curve shape is not reproducible. A slight variation in the growing conditions may result in strong changes in the morphology, microstructure, and surface-impurity-related defects, considerably affecting the TL glow curve features. In order to study the main TL characteristics under controlled growing conditions, we present results on three 0.5, 1.0, and 4.0 m thick hot filament CVD (HFCVD) diamond films grown on Si (100) substrates. The recorded TL glow curves were resolved into individual peaks by a home-made deconvolution program and the kinetic parameters of the peaks were extracted. The best fits of the TL glow curves were obtained using four pe...
Production and testing of a synthetic diamond film radiation dosimeter for radiotherapy
A detector, constituted by a polycrystalline chemical vapor deposited diamond film, has been made for on-line radiotherapy beam analysis in terms of dose distributions in water equivalent material. Preliminary results are reported which evidence that the leakage current can be a limiting parameter for an efficient collection of the charge carriers produced by the ionizing radiation. A signal to noise ratio near to 100 has been obtained. A priming effect similar to that found in natural diamond devices has also been evidenced, and a stable detector response was obtained after an accumulated dose of 5 Gy. The linearity has been achieved between the detector reading and the dose. The detector sensitivity resulted was equal to 77 nC/Gy per mm sup 3 of detector sensitive volume. A power law with exponent DELTA less than one has been found between detector reading and dose rate. However, when the dose rate dependence was corrected, the percentage depth doses, along an X-ray beam central axis, was in agreement with those obtained by an ionization chamber.
Website Policies and Important Links Comments
 |
 |
 |
WorldWideScience.org is maintained by the
U.S. Department of Energy's
Office of Scientific and Technical Information as the Operating Agent
for the WorldWideScience Alliance.