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Friction and wear performance of diamondlike carbon films grown in various source gas plasmas

Description: In this study, the authors investigated the effects of various source gases (methane, ethane, ethylene, and acetylene) on the friction and wear performance of diamondlike carbon (DLC) films prepared in a plasma enhanced chemical vapor deposition (PECVD) system. Films were deposited on AISI H13 steel substrates and tested in a pin-on-disk machine against DLC-coated M50 balls in dry nitrogen. They found a close correlation between friction coefficient and source gas composition. Specifically, films grown in source gases with higher hydrogen-to-carbon ratios exhibited lower friction coefficients and higher wear resistance than films grown in source gases with lower hydrogen-to-carbon (H/C) ratios. The lowest friction coefficient (0.014) was achieved with a film derived from methane with an WC ratio of 4, whereas the coefficient of films derived from acetylene (H/C = 1) was of 0.15. Similar correlations were observed for wear rates. Specifically, films derived from gases with lower H/C values were worn out and the substrate material was exposed, whereas films from methane and ethane remained intact and wore at rates that were nearly two orders of magnitude lower than films obtained from acetylene.
Date: January 18, 2000
Creator: Erdemir, A.; Nilufer, I. B.; Eryilmaz, O. L.; Beschliesser, M. & Fenske, G. R.
Partner: UNT Libraries Government Documents Department

Species-resolved imaging and gated photon counting spectroscopy of laser ablation plume dynamics during KrF- and ArF-laser PLD of amorphous diamond films

Description: Gated photon counting spectroscopy and species-resolved ICCD photography were used to study the weak plasma luminescence following the propagation of the initial ablation plume in vacuum and during the rebound of the plume with a substrate during pulsed laser deposition of amorphous diamond. These methods techniques were required in order to investigate notable differences between amorphous diamond-like carbon films formed by pulsed laser deposition from ArF (193 nm) and KrF (248 nm) irradiation of pyrolytic graphite in vacuum. Three principal regions of plume emission were found: (1) a bright luminescent ball (v {approximately}3--5 cm/{mu}s) displaying nearly entirely C{sup +} emission which appears to result from laser interaction with the initial ejecta, (2) a spherical ball of emission (v {approximately} 1 cm/{mu}s) displaying neutral carbon atomic emission lines and, at early times, jets of excited C{sub 2}, and (3) a well-defined region of broadband emission (v {approximately} 0.3 cm/{mu}s) near the target surface first containing emission bands from C{sub 2}, then weak, continuum emission thought to result from C{sub 3} and higher clusters and/or blackbody emission from hot clusters or nanoparticles.
Date: December 1, 1995
Creator: Geohegan, D.B. & Puretzky, A.A.
Partner: UNT Libraries Government Documents Department

High rate PLD of diamond-like-carbon utilizing high repetition rate visible lasers

Description: Pulsed Laser Deposition (PLD) has been shown to be an effective method for producing a wide variety of thin films of high-value-added materials. The high average powers and high pulse repetition frequencies of lasers under development at LLNL make it possible to scale-up PLD processes that have been demonstrated in small systems in a number of university, government, and private laboratories to industrially meaningful, economically feasible technologies. A copper vapor laser system at LLNL has been utilized to demonstrate high rate PLD of high quality diamond-like-carbon (DLC) from graphite targets. The deposition rates for PLD obtained with a 100 W laser were {approx} 2000 {mu}m{center_dot}cm{sup 2}/h, or roughly 100 times larger than those reported by chemical vapor deposition (CVD) or physical vapor deposition (PVD) methods. Good adhesion of thin (up to 2 pm) films has been achieved on a small number of substrates that include SiO{sub 2} and single crystal Si. Present results indicate that the best quality DLC films can be produced at optimum rates at power levels and wavelengths compatible with fiber optic delivery systems. If this is also true of other desirable coating systems, this PLD technology could become an extremely attractive industrial tool for high value added coatings.
Date: September 15, 1994
Creator: McLean, W. II; Fehring, E.J.; Dragon, E.P. & Warner, B.E.
Partner: UNT Libraries Government Documents Department

Friction and wear properties of smooth diamond films grown in fullerene-argon plasmas

Description: In this study, we describe the growth mechanism and the ultralow friction and wear properties of smooth (20-50 nm rms) diamond films grown in a microwave plasma consisting of Ar and fullerene (the carbon source). The sliding friction coefficients of these films against Si{sub 3}N{sub 4} balls are 0.04 and 0.1 in dry N{sub 2} and air, which are comparable to that of natural diamond sliding against the same pin material, but is lower by factors of 5 to 10 than that afforded by rough diamond films grown in conventional H{sub 2}-CH{sub 4} plasmas. Furthermore, the smooth diamond films produced in this work afforded wear rates to Si{sub 3}N{sub 4} balls that were two to three orders of magnitude lower than those of H{sub 2}-CH{sub 4} grown films. Mechanistically, the ultralow friction and wear properties of the fullerene-derived diamond films correlate well with their initially smooth surface finish and their ability to polish even further during sliding. The wear tracks reach an ultrasmooth (3-6 nm rms) surface finish that results in very little abrasion and ploughing. The nanocrystalline microstructure and exceptionally pure sp{sup 3} bonding in these smooth diamond films were verified by numerous surface and structure analytical methods, including x-ray diffraction, high-resolution AF-S, EELS, NEXAFS, SEM, and TEM. An AFM instrument was used to characterize the topography of the films and rubbing surfaces.
Date: August 1, 1995
Creator: Erdemir, A.; Fenske, G.R.; Bindal, C.; Zuiker, C.; Krauss, A.R. & Gruen, D.M.
Partner: UNT Libraries Government Documents Department

Dymalloy: A composite substrate for high power density electronic components

Description: High power density electronic components such as fast microprocessors and power semiconductors must operate below the maximum rated device junction temperature to ensure reliability. function temperatures are determined by the amount of heat generated and the thermal resistance from junction to the ambient thermal environment. Two of the Largest contributions to this thermal resistance are the die attach interface and the package base. A decrease in these resistances can allow increased component packing density in MCMs, reduction of heat sink volume in tightly packed systems, enable the use of higher performance circuit components, and improve reliability. The substrate for high power density devices is the primary thermal link between the junctions and the heat sink. Present high power multichip modules and single chip packages use substrate materials such as silicon nitride or copper tungsten that have thermal conductivity in the range of 200 W/mK. We have developed Dymalloy, a copper-diamond composite, that has a thermal conductivity of 420 W/mK and an adjustable coefficient of thermal expansion, nominally 5.5 ppm/C at 25 C, compatible with silicon and gallium arsenide. Because of the matched coefficient of thermal expansion it is possible to use low thermal resistance hard die attach methods. Dymalloy is a composite material made using micron size Type I diamond powder that has a published thermal conductivity of 600 to 1000 W/mK in a metal matrix that has a thermal conductivity of 350 W/mK. The region of chemical bonding between the matrix material and diamond is limited to approximately 1000 A to maintain a high effective thermal conductivity for the composite. The material may be fabricated in near net shapes. Besides having exceptional thermal properties, the mechanical properties of this material also make it an attractive candidate as an electronic component substrate material.
Date: June 29, 1995
Creator: Kerns, J.A.; Colella, N.J.; Makowiecki, D. & Davidson, H.L.
Partner: UNT Libraries Government Documents Department

Diamond switches for high temperature electronics

Description: Diamond switches are well suited for use in high temperature electronics. Laboratory feasibility of diamond switching at 1 kV and 18 A was demonstrated. DC blocking voltages up to 1 kV were demonstrated. A 50 {Omega} load line was switched using a diamond switch, with switch on-state resistivity {approx}7 {Omega}-cm. An electron beam, {approx}150 keV energy, {approx}2 {mu}s full width at half maximum was used to control the 5 mm x 5 mm x 100 {mu}m thick diamond switch. The conduction current temporal history mimics that of the electron beam. These data were taken at room temperature.
Date: April 25, 1996
Creator: Prasad, R.R.; Rondeau, G. & Qi, Niansheng
Partner: UNT Libraries Government Documents Department

Diamond and diamond-like carbon films for advanced electronic applications

Description: 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.
Date: March 1, 1996
Creator: Siegal, M.P.; Friedmann, T.A. & Sullivan, J.P.
Partner: UNT Libraries Government Documents Department

Dynamics of laser ablation for thin film growth by pulsed laser deposition

Description: Fundamental gas dynamic and laser-material interactions during pulsed laser deposition are explored through sensitive imaging and plasma spectroscopic diagnostics. Two recent phenomena, plume-splitting in background gases and the unusual dynamics of graphite ablation for amorphous diamond film growth, are presented.
Date: February 1, 1996
Creator: Geohegan, D.B. & Puretzky, A.A.
Partner: UNT Libraries Government Documents Department

First-principles study of {pi}-bonded (100) planar defects in diamond.

Description: A periodic density functional study of the high-energy {pi}-bonded (100) stacking fault in diamond that can serve as a prototype of a twist grain boundary has been carried out. Information on formation energies, geometries and the electronic structure has been obtained. A single point electronic structure calculation of a {Sigma}5 twist grain boundary based on the geometry taken from a molecular dynamics simulation has also been performed.
Date: December 16, 1998
Creator: Zapol, P.
Partner: UNT Libraries Government Documents Department

Grain boundaries and grain size distributions in nanocrystalline diamond films derived from fullerene precursors

Description: Film growth from C{sub 60}/Ar mixtures results in very pure diamond. Diamond films grown using C{sub 60} as a carbon source have been shown to be nanocrystalline with average grain sizes of 15 nm and standard deviations of 13 nm. The measured grain size distribution for two separate films, each based on measurements of over 400 grains, were found to be very similar and well approximated by a gamma distribution. Unlike typical CVD grown diamond films, these nanocrystalline films do not exhibit columnar growth. From the measured grain size distributions, it is estimated that 2% of the carbon atoms are located in the grain boundaries. The structure of the carbon in the grain boundaries is not known, but the films survive extended wear tests and hold together when the substrate is removed, indicating that the grains are strongly bound. The grain boundary carbon may give rise to additional features in the Raman spectrum and result in absorption and scattering of light in the films. We also expect that the grain boundary carbon may affect film properties, such as electrical and thermal conductivity.
Date: December 31, 1995
Creator: Csencsits, R.; Zuiker, C.D.; Gruen, D.M. & Krauss, A.R.
Partner: UNT Libraries Government Documents Department

Dynamical studies of periodic and disordered systems

Description: The time evolution of two classes of systems is studied with real time molecular dynamics simulations. The first consists of a coupled electron-lattice system. For a periodic system, we present results for the time evolution of a one-dimensional system consisting of an electron, described by a tight-binding Hamiltonian, and a harmonic lattice, coupled by a deformation-type potential. We solve numerically the nonlinear system of equations of motion for this model in order to study the effects of varying the electronic effective mass for several initial conditions and coupling strengths. A large effective mass favors localized polaron formation for initially localized electrons. For initially extended electronic states, increasing the effective mass of an electron initially close to the bottom of the band makes localization more difficult, while for an initially highly excited electronlocalized polaron formation is possible only when the electronic effective mass and the atomic masses of the lattice become of the same order.
Date: November 1, 1995
Creator: Kopidakis, G.
Partner: UNT Libraries Government Documents Department

Copper-diamond composite substrates for electronic components

Description: High-power density electronic components such as fast microprocessors and power semiconductors are often limited by inability to keep the device junctions below their max rated operating temperature. Present high power multichip module and single chip package designs use substrate materials such as Si nitride or copper tungsten with thermal conductivity in the range of 200 W/m{center_dot}K. We have developed a copper-diamond composite (Dymalloy) with a thermal conductivity of 420 W/m{center_dot}K, better than Cu, and an adjustable thermal expansion coefficient (TCE=5.5 ppM/C at 25 C), compatible with Si and GaAs. Because of the matched TCE, it is possible to use low thermal resistance hard die attach methods. The mechanical properties of the composite also make it attractive as an electronic component substrate material.
Date: January 25, 1995
Creator: Davidson, H.L.; Colella, N.J.; Kerns, J.A. & Makowiecki, D.
Partner: UNT Libraries Government Documents Department

The Crater of Diamonds: A History of the Pike County, Arkansas, Diamond Field, 1906-1972

Description: The first diamond mine in North America was discovered in 1906 when John W. Huddleston found two diamonds on his farm just south of Murfreesboro in Pike County, Arkansas. Experts soon confirmed that the diamond-bearing formation on which Huddleston made his discovery was the second largest of its kind and represented 25 percent of all known diamond-bearing areas in the world. Discovery of the field generated nearly a half century of speculative activity by men trying to demonstrate and exploit its commercial viability. The field, however, lacked the necessary richness for successful commercial ventures, and mining was eventually replaced in the early 1950s by tourist attractions that operated successfully until 1972. At that time the State of Arkansas purchased the field and converted it to a state park. Thus this work tell the rich and complicated story of America'a once and only diamond field, analyzes the reasons for the repeated failures of efforts to make it commercially viable, and explains how it eventually succeeded as a tourist venture.
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Date: May 2002
Creator: Henderson, John C.
Partner: UNT Libraries

Subsurface structure in polished fused silica and diamond turned single crystal silicon

Description: The surface and near surface structure of glass and other optical materials is greatly influenced by the nature of the processes used to generate that surface. In high quality optics, the effects of process changes are often subtle and cannot be seen with conventional metrology. The presence of process induced damage in the near surface region is felt in a number of ways. Damage thresholds for optics subjected to high fluences are a particular problem in UV or high-powered laser systems. In high quality glass, the chemical and material composition of the outermost layer is influenced principally by the grinding, lapping and polishing processes used in fabrication. Performance in high fluence applications is often dominated by these process-induced inhomogeneities in the first few hundred nanometers of material. Each succeeding step in a process is designed to remove the damage from the previous operation. However, any force against the surface, no matter how slight will leave evidence of damage. Fabrication processes invariably create dislocations, cracks and plastic deformation between 100 nm and 500 nm below the surface. In glass polishing, the first 100 nm is comprised of material redeposited from the polishing solution. This redeposition layer is responsible for the extremely smooth surfaces that can be generated on glass. Unfortunately, this layer also conceals many flaws present in the deeper surface regions.
Date: June 1, 1999
Creator: Carr, J W; Fearon, E; Haack, J; Hoskins, S; Hutcheon, I & Summers, L
Partner: UNT Libraries Government Documents Department

Diamond monochromators for APS undulator-A beamlines

Description: There has been considerable interest in the use of diamonds in high heat load monochromators (HHLMs) in the last several years. The superb thermal and mechanical properties of single crystal diamonds serve to minimize distortions caused by a given thermal load, while the low x-ray absorption cross-section reduces both the total power deposited in the crystal as well as the peak (volumetric) power density. The primary obstacle for the widespread use of diamonds at present is a lack of ready availability of perfect single crystals of the desired size and orientation. Although it is possible to obtain near-perfect natural diamonds of the size and orientation required for use on an undulator beamline, the selection process is generally one of trial and error. Near perfect synthetic diamonds can currently be obtained in the minimum necessary size (typically 4-5 mm on a side). A collaborative agreement has been made between the staff of the Advanced Photon Source (APS), the European Synchrotron Radiation Facility (ESRF), and the Super Photon Ring-8 GeV (SPring-8) to explore the use of diamonds as high heat load monochromators and is on-going. One of the avenues of research is to push for improved perfection and size of synthetic diamonds. Sumitomo Electric Corporation of Japan has agreed to work with staff from SPring-8 to grow [100] oriented perfect single crystal diamonds of 10 x 10 x 1 mm{sup 3} size by 1996/1997 (from which one could also cut pieces with the large face parallel to the (111) planes). They have taken the first step in producing an essentially perfect 4 x 4 x 1 mm{sup 3} type II diamond with less than 5 {mu}rad (1 arc second) strain (measured over the entire surface). The authors believe progress in the production of synthetic diamonds, as well as improvement in ties with ...
Date: September 1, 1995
Creator: Blasdell, R.C.; Assoufid, L.A. & Mills, D.M.
Partner: UNT Libraries Government Documents Department

Sub-nanometer interferometry and precision turning for large optical fabrication

Description: At Lawrence Livermore National Laboratory (LLNL), we have the unique combination of precision turning and metrology capabilities critical to the fabrication of large optical elements. We have developed a self-referenced interferometer to measure errors in aspheric optics to sub- nanometer accuracy over 200-millimeter apertures, a dynamic range of 5{approximately}10. We have utilized diamond turning to figure optics for X-ray to IR wavelengths and, with fast-tool-servo technology, can move optical segments from off-axis to on-axis. With part capacities to 2.3-meters diameter and the metrology described above, segments of very large, ultra-lightweight mirrors can potentially be figured to final requirements. precision of diamond-turning will carryover although the surface finish may be degraded. Finally, the most critical component of a fabrication process is the metrology that enables an accurate part. Well characterized machines are very repeatable and part accuracy must come from proper metrology. A self- referencing interferometer has been developed that can measure accurately to sub-nanometer values. As with traditional interferometers, measurements are fast and post- processed data provides useful feedback to the user. The simplicity of the device allows it to be used on large optics and systems.
Date: April 1, 1999
Creator: Klingmann, J L & Sommargren, G E
Partner: UNT Libraries Government Documents Department

Grain boundaries and mechanical properties of nanocrystalline diamond films.

Description: Phase-pure nanocrystalline diamond thin films grown from plasmas of a hydrogen-poor carbon argon gas mixture have been analyzed regarding their hardness and elastic moduli by means of a microindentor and a scanning acoustic microscope.The films are superhard and the moduli rival single crystal diamond. In addition, Raman spectroscopy with an excitation wavelength of 1064 nm shows a peak at 1438 l/cm and no peak above 1500 l/cm, and X-ray photoelectron spectroscopy a shake-up loss at 4.2 eV. This gives strong evidence for the existence of solitary double bonds in the films. The hardness and elasticity of the films then are explained by the assumption, that the solitary double bonds interconnect the nanocrystals in the films, leading to an intergrain boundary adhesion of similar strength as the intragrain diamond cohesion. The results are in good agreement with recent simulations of high-energy grain boundaries.
Date: August 6, 1999
Creator: Busmann, H.-G.; Pageler, A. & Gruen, D. M.
Partner: UNT Libraries Government Documents Department

Luminosity monitor.

Description: Luminosity monitors are needed in each experiment doing spin physics at RHIC. They concentrate on the luminosity aspects here because, for example, with a 10{sup {minus}3} raw asymmetry in an experiment, an error of 10{sup {minus}4} in the luminosity is as significant as a 10% polarization error. Because luminosity is a property of how two beams overlap, the luminosity at an interaction region must be measured at that interaction region in order to be relevant to the experiment at that interaction region. The authors will have to do the physics and the luminosity measurements by using labels on the event sums according to the polarization labels on the colliding bunches. Most likely they will not have independent polarization measurement on each bunch, but only on all the filled bunches in a ring, or perhaps all the bunches that are actually used in an experiment. Most analyses can then be handled by using the nine combinations gotten from three kinds of bunches in each ring, +, {minus} and empty bunches. The empty bunches are needed to measure beam-gas background, (and some, like six in a row, are needed for the beam abort). Much of the difficulty comes from the fact that they must use a physics process to represent the luminosity. This process must have kinematic and geometric cuts both to reduce systematics such as beam-gas backgrounds, and to make it representative of the part of the interaction diamond from which the physics events come.
Date: July 16, 1998
Creator: Underwood, D. G.
Partner: UNT Libraries Government Documents Department

Nucleation of nanocrystalline diamond by fragmentation of fullerene precursors.

Description: Growth of diamond films from C{sub 60}/Ar microwave discharges results in a nanocrystalline microstructure with crystallite sizes in the range 3-10 nm. Heterogeneous nucleation rates of 10{sup 10} cm{sup {minus}2} sec are required to account for the results. The nucleation mechanism presented here fulfills this requirement and is based on the insertion of carbon dimer, C{sub 2}, molecules, produced by fragmentation of C{sub 60}, into the n-bonded dimer rows of the reconstructed (100) surface of diamond. Density functional theory is used to calculate the energetic of C{sub 2} insertion into carbon clusters that model the (100) surface. The reaction of singlet C{sub 2} with the double bond of the C{sub 9}H{sub 12} cluster leads to either carbene structures or a cyclobutynelike structure. At the HF/6-31G* level, the carbene product has a C{sub 2v} structure, while at the B3LYP/6-31G* levels of theory, it has a C{sub s} structure with the inserted C{sub 2} tilted. No barrier for insertion into the C=C double bond of the C{sub 9}H{sub 12} cluster was found at the HF/6-31G* and B3LYP/6-31G* levels of theory. Thus, calculations including correlation energy and geometry optimization indicate that insertion of C{sub 2} into a C=C double bond leads to a large energy lowering, {approximately}120 kcal/mol for a C{sub 9}H{sub 12} cluster, and there is no barrier for insertion.
Date: May 4, 1998
Creator: Gruen, D. M.
Partner: UNT Libraries Government Documents Department

OPTIMIZATION OF DEEP DRILLING PERFORMANCE--DEVELOPMENT AND BENCHMARK TESTING OF ADVANCED DIAMOND PRODUCT DRILL BITS & HP/HT FLUIDS TO SIGNIFICANTLY IMPROVE RATES OF PENETRATION

Description: The industry cost shared program aims to benchmark drilling rates of penetration in selected simulated deep formations and to significantly improve ROP through a team development of aggressive diamond product drill bit--fluid system technologies. Overall the objectives are as follows: Phase 1--Benchmark ''best in class'' diamond and other product drilling bits and fluids and develop concepts for a next level of deep drilling performance; Phase 2--Develop advanced smart bit-fluid prototypes and test at large scale; and Phase 3--Field trial smart bit-fluid concepts, modify as necessary and commercialize products. As of report date, TerraTek has concluded all major preparations for the high pressure drilling campaign. Baker Hughes encountered difficulties in providing additional pumping capacity before TerraTek's scheduled relocation to another facility, thus the program was delayed further to accommodate the full testing program.
Date: October 1, 2004
Creator: Black, Alan & Judzis, Arnis
Partner: UNT Libraries Government Documents Department

Tribology and coatings

Description: The future use of fuel-efficient, low-emission, advanced transportation systems (for example, those using low-heat-rejection diesel engines or advanced gas turbines) presents new challenges to tribologists and materials scientists. High service temperatures, corrosive environments, and extreme contact pressures are among the concerns that make necessary new tribological designs, novel materials, and effective lubrication concepts. Argonne is working on methods to reduce friction, wear and corrosion, such as soft metal coatings on ceramics, layered compounds, diamond coatings, and hard surfaces.
Date: June 1995
Partner: UNT Libraries Government Documents Department

Performance Study of Scepter<sup>TM</sup> Metal Bond Diamond Grinding Wheel

Description: Advanced ceramics are attractive for many applications in the transportation, energy, military, and industrial markets because they possess properties of high-temperature durability, corrosion resistance, strength, hardness, stiffness, and wear resistance. Unfortunately, these same properties make advanced ceramics more difficult to machine than traditional materials. The reliability and manufacturing costs of advanced ceramic components are significant concerns that must be overcome. Nevertheless, the use of advanced ceramic materials is expected to increase dramatically in new transportation systems in response to more stringent energy conservation and pollution reduction requirements. This study discusses the goals, commercialization plans, phased development, scale-up, testing, and external verification of performance of the innovative grinding wheel that evolved from the project.
Date: June 17, 1999
Creator: Denison, S.K.; Licht, R.W.; McSpadden, S.B., Jr.; Parten, R.J.; Picone, J.W. & Shelton, J.E.
Partner: UNT Libraries Government Documents Department

Point Defect Incorporation During Diamond Chemical Vapor Deposition

Description: The incorporation of vacancies, H atoms, and sp{sup 2} bond defects into single-crystal homoepitaxial (100)(2x1)- and(111)-oriented CVD diamond was simulated by atomic-scale kinetic Monte Carlo. Simulations were performed for substrate temperatures from 600 C to 1200 C with 0.4% CH{sub 4} in the feed gas, and for 0.4% to 7% CH{sub 4} feeds with a substrate temperature of 800 C. The concentrations of incorporated H atoms increase with increasing substrate temperature and feed gas composition, and sp{sup 2} bond trapping increases with increasing feed gas composition. Vacancy concentrations are low under all conditions. The ratio of growth rate to H atom concentration is highest around 800-900 C, and the growth rate to sp{sup 2} ratio is maximum around 1% CH{sub 4}, suggesting that these conditions are ideal for economical diamond growth under the simulated conditions.
Date: August 2, 1999
Creator: Battaile, C.C.; Srolovitz, D.J. & Butler, J.E.
Partner: UNT Libraries Government Documents Department