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Showing papers on "Diamond published in 1991"


Journal ArticleDOI
Massimo V. Fischetti1
TL;DR: In this article, Monte Carlo simulations of electron transport in seven semiconductors of the diamond and zinc-blende structure (Ge, Si, GaAs, InP, AlAs, AlP, InAs, GaP) and some of their alloys were performed at two lattice temperatures (77 and 300 K).
Abstract: Monte Carlo simulations of electron transport in seven semiconductors of the diamond and zinc-blende structure (Ge, Si, GaAs, InP, AlAs, InAs, GaP) and some of their alloys (Al/sub x/Ga/sub 1-x/As, In/sub x/Ga/sub 1-x/As, Ga/sub x/In/sub 1-x/P) and hole transport in Si were performed at two lattice temperatures (77 and 300 K). The model uses band structures obtained from local empirical pseudopotential calculations and particle-lattice scattering rates computed from the Fermi golden rule to account for band-structure effects. Intervalley deformation potentials significantly lower than those which have been previously reported are needed to reproduce available experimental data. This is attributed to the more complicated band structures, particularly around the L- and X-symmetry points in most materials. Satisfactory agreement is obtained between Monte Carlo results and some experiments. >

572 citations


Journal ArticleDOI
TL;DR: In this paper, a predeposition process of several minutes duration was introduced in which a high methane fraction in the feed gas was used and in which negative bias voltage was applied to the substrate.
Abstract: Generation of diamond nuclei has been realized on a silicon mirror surface in plasma chemical vapor deposition. Prior to the normal diamond growth process, a predeposition process of several minutes duration was introduced in which a high methane fraction in the feed gas was used and in which a negative bias voltage was applied to the substrate. This resulted in an enormous enhancement of the generation of diamond nuclei. For the onset of diamond nucleation the minimum voltage was −70 V and the minimum methane fraction in the methane‐hydrogen feed gas was 5%. Density of a diamond nuclei as high as 1010/cm2 was attained with this method.

542 citations


Journal ArticleDOI
TL;DR: In this paper, a C H O phase diagram is introduced providing a common scheme for all major diamond chemical vapour deposition (CVD) methods used to date, revealing that low pressure diamond synthesis is only feasible within a well-defined field of the phase diagram, a diamond domain that allows general predictions of gas phase compositions and starting materials suitable for diamond synthesis.

472 citations


Journal ArticleDOI
01 Aug 1991-Nature

413 citations



Journal ArticleDOI
C. Wang1, A. Garcia1, David C. Ingram1, M. Lake1, Martin E. Kordesch1 
TL;DR: In this paper, a self-emitting CVD polycrystalline diamond film was observed to emit electrons with an intensity sufficient to form an image in the accelerating field of an emission microscope without external excitation.
Abstract: Thick (100 μm) chemical vapour deposited (CVD) polycrystalline diamond films have been observed to emit electrons with an intensity sufficient to form an image in the accelerating field of an emission microscope without external excitation (> 3 MV/m). The individual crystallites are of the order of 1–10 μm. The combined crystallite diameter and the electric field strength in these ‘self-emitting’ films are far below those typical for cold field emitters.

392 citations


Journal ArticleDOI
01 May 1991
TL;DR: The potential of SiC and diamond for producing microwave and millimeter-wave electronic devices is reviewed in this article, where it is shown that both of these materials possess characteristics that may permit RF electronic devices with performance similar to or greater than what is available from devices fabricated from the commonly used semiconductors, Si, GaAs, and InP.
Abstract: The potential of SiC and diamond for producing microwave and millimeter-wave electronic devices is reviewed. It is shown that both of these materials possess characteristics that may permit RF electronic devices with performance similar to or greater than what is available from devices fabricated from the commonly used semiconductors, Si, GaAs, and InP. Theoretical calculations of the RF performance potential of several candidate high-frequency device structures are presented: the metal semiconductor field-effect transistor (MESFET), the impact avalanche transit-time (IMPATT) diode, and the bipolar junction transistor (BJT). Diamond MESFETs are capable of producing over 200 W of X-band power as compared to about 8 W for GaAs MESFETs. Devices fabricated from SiC should perform between these limits. Diamond and SiC IMPATT diodes also are capable of producing improved RF power compared to Si, GaAs, and InP devices at microwave frequencies. RF performance degrades with frequency and only marginal improvements are indicated at millimeter-wave frequencies. Bipolar transistors fabricated from wide bandgap material probably offer improved RF performance only at UHF and low microwave frequencies. >

368 citations


Journal ArticleDOI
TL;DR: In this article, current densities of 0.1 to 1 A-cm/sup -2/ are estimated for a diode current of 10 mA for a Si cold cathode.
Abstract: Diamond cold cathodes have been formed by fabricating mesa-etched diodes using carbon ion implantation into p-type diamond substrates. When these diodes are forward biased, current is emitted into vacuum. The cathode efficiency (emitted current divided by diode current) varies from 2*10/sup -4/ to 1*10/sup -10/ and increases with the addition of 10/sup -2/-torr partial pressure of O/sub 2/ into the vacuum system. Current densities of 0.1 to 1 A-cm/sup -2/ are estimated for a diode current of 10 mA. This compares favorably with Si cold cathodes (not coated with Cs), which have efficiencies of approximately 2*10/sup -5/ and current densities of approximately 2*10/sup -2/ A-cm/sup -2/. It is believed that higher current densities and efficiencies can be obtained with more efficient cathode designs and an ultrahigh-vacuum environment. >

342 citations


Journal ArticleDOI
TL;DR: In this paper, the potential n-type dopants in diamond were investigated via ab initio methods and the well-known distortions around the deep donor N were found to arise from the interaction of the N lone pair with a C dangling bond.
Abstract: Potential n-type dopants in diamond are investigated via ab initio methods. The well-known distortions around the deep donor N are found to arise from the interaction of the N lone pair with a C dangling bond. P, Li, and Na are all shallow dopants, but their solubilities are muh too low for doping via in-diffusion. Li is a relatively fast diffuser, Na is stable up to moderate temperatures, while P should remain immobile even at high temperatures. Na, being an interstitial dopant, is particularly suitable for ion implantation, since there is no need to displace host atoms.

305 citations


Patent
15 Apr 1991
TL;DR: In this article, a rock bit button of cemented carbide for percussive or rotary crushing rock drilling is presented, which is provided with one or more bodies of polycrystalline diamond in the surface produced at high pressure and high temperature in the diamond stable area.
Abstract: The present invention relates to a rock bit button of cemented carbide for percussive or rotary crushing rock drilling. The button is provided with one or more bodies of polycrystalline diamond in the surface produced at high pressure and high temperature in the diamond stable area. Each diamond body is completely surrounded by cemented carbide except the top surface.

266 citations


Book
01 Jan 1991
TL;DR: Diamonds today The Structure of Diamond Impurities in diamond Optical absorption and colour Luminescence The morphology of diamond Geometric defects in the diamond lattice Mechanical properties Strength and fracture Plastic deformation of diamond Polishing and shaping diamond Mechanical differences between diamonds Friction Polycrystaline diamond (PCD) Applications and Wear of Diamond Wear and surface characteristics Turning, boring and milling Grinding Sawing and drilling Micellaneous applications Appendix 1 Some numerical values Appendix 2 Units and conversion factors
Abstract: Diamonds today The Structure of Diamond Impurities in diamond Optical absorption and colour Luminescence The morphology of diamond Geometric defects in the diamond lattice Mechanical properties Strength and fracture Plastic deformation of diamond Polishing and shaping diamond Mechanical differences between diamonds Friction Polycrystaline diamond (PCD) Applications and Wear of Diamond Wear and surface characteristics Turning, boring and milling Grinding Sawing and drilling Micellaneous applications Appendix 1 Some numerical values Appendix 2 Units and conversion factors

Journal ArticleDOI
TL;DR: The frequency and line shape of the diamond Raman line are examined in detail for a series of microwave-plasma-assisted chemical-vapor-deposition films grown on Si and it is concluded that the observed shifts do notmore arise from phonon confinement alone and arise primarily from compressive stress.
Abstract: The frequency and line shape of the diamond Raman line are examined in detail for a series of microwave-plasma-assisted chemical-vapor-deposition films grown on Si. The Raman lines in the films appear at higher frequency (shifts of up to 3 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$) than that of natural diamond and the observed lines are symmetric with broader linewidths than that of natural diamond, ranging from 5.7 to 17.1 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$. In addition, the line frequencies and linewidths are correlated; the films with the highest vibrational frequencies have the largest linewidths. The data include single-point measurements on eight films grown under different conditions as well as 500 data points from different positions on a single film that were obtained in a spatially resolved Raman experiment. Several mechanisms for the frequency shift and the correlation of the linewidth with frequency are considered including phonon confinement, residual stress, and defect scattering. Contrary to the observations, Raman line shapes computed from the phonon-confinement model (which has been used successfully to model Raman scattering in microcrystalline Si and GaAs), using phonon-dispersion curves for diamond from the literature, are highly asymmetric at the linewidths observed. It is concluded that the observed shifts in the diamond Raman line do not arise from phonon confinement alone and arise primarily from compressive stress. The line broadening also is not produced by phonon confinement alone and may arise from decreasing phonon lifetime associated with scattering from defects or from an inhomogeneous stress distribution in the films. The observed correlation between Raman line frequency and width suggests that the degree of compressive stress may be associated with the density of microcrystalline defects.

Journal ArticleDOI
TL;DR: In this article, a model for the condensation of energetic carbon atoms into diamond-like films in which a quench-type surface accommodation mechanism is operative is proposed, and the degree of diamondlike film character is found to depend upon the deposition technique as well as the substrate temperature and thermal diffusivity.
Abstract: Trends in recently reported data on high sp3 fraction (up to 85%), nonhydrogenated amorphous diamond‐like carbon films deposited by ion beam sputtering and laser vaporization are examined. The degree of diamondlike film character is found to depend upon the deposition technique as well as the substrate temperature and thermal diffusivity. The data suggest that the combination of incident particle kinetic energy and surface accommodation determine the physical properties of the resultant film. A model is proposed for the condensation of energetic carbon atoms into diamondlike films in which a quench‐type surface accommodation mechanism is operative.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the tensile and compressive total (thermal and intrinsic) stress in diamond films prepared by microwave plasma CVD, as a function of methane concentration (0.2% −3.0%) and deposition temperature (600-900°C).
Abstract: The stress in diamond films prepared by microwave plasma CVD was investigated as a function of methane concentration (0.2%–3.0%) and deposition temperature (600–900 °C). Tensile and compressive total (thermal and intrinsic) stress were observed, depending on the deposition conditions. The thermal stress is compressive and relatively constant (0.215–0.275 GPa) over the temperature range investigated. The intrinsic stress is tensile and its origin is interpreted in terms of the grain boundary relaxation model. Calculations indicate a value of 0.84 GPa, using the grain boundary model, which is in fair agreement with the measured value. For the methane series, the tensile intrinsic stress decreases with increasing the methane fraction. The increasing compressive stress is ascribed to increased impurity (hydrogen and nondiamond phase carbon) incorporation with increasing methane fraction. 15N nuclear reaction analysis shows a linear correlation between hydrogen in the film and methane in the supply gas while spectroscopic ellipsometry shows a direct correlation between optically absorbing nondiamond (sp2) carbon incorporation and methane. For the temperature series, the intrinsic tensile stress increases with deposition temperature. The increase is ascribed to decreasing sp2 C incorporation with temperature, as confirmed by spectroscopic ellipsometry measurements.

Journal ArticleDOI
TL;DR: In this paper, an experimental results of ultra-precision diamond turning of stainless steel were presented, where ultrasonic vibration of 40 kHz was applied to a single crystal diamond tool in the cutting direction.

Patent
04 Jun 1991
TL;DR: In this article, a diamond thrust bearing and a method for manufacturing it is presented, wherein diamond bearing pads are interference fitted at ambient temperatures into a plurality of equidistantly spaced bearing pad recesses located in a circle in a receiving surface of a bearing pad retainer.
Abstract: A diamond thrust bearing and method for manufacturing the diamond thrust bearing wherein diamond bearing pads are interference fitted at ambient temperatures into a plurality of equidistantly spaced bearing pad recesses located in a circle in a receiving surface of a bearing pad retainer. The bearing faces of the diamond bearing pads are located coplanar with a predetermined common bearing plane by pressing the bearing faces into the bearing pad retainer with a ram and inflexible pressing plate until the pressing face of the pressing plate is stopped by a press stop block. The diamond thrust bearing manufactured using the method will be free from heat induced stresses that cause bearing face misalignment.

Journal ArticleDOI
TL;DR: In this article, the structural, optical, electrical and physical properties of amorphous carbon deposited from the filtered plasma stream of a vacuum arc were investigated, and the tetrahedral coordination of the material was confirmed by measurements of stress and plasmon energy as a function of ion energy.

Journal ArticleDOI
TL;DR: In this article, a tool post and chuck with constrained liquid nitrogen flows has been constructed for diamond tool wear reduction at cryogenic machining at high temperatures. But the results show that tool wear is extremely rapid when ferrous materials are diamond turned.

01 Jan 1991
TL;DR: In this article, the following topics were discussed: Vapor phase diamonds, general, theory, modeling, natural and synthetic HP/HT diamond, gas phase and surface measurements, gas phases and surface chemistry, properties: Mechanical, chemical, thermal properties, electrical, and diamond-like materials; and Cubic boron nitride.
Abstract: This book covers the following topics: Vapor phase diamonds; General, theory, modeling; Natural and synthetic HP/HT diamond; Gas phase and surface measurements; Gas phase and surface chemistry; Properties: Mechanical, chemical, thermal; Properties: Electrical; Diamond-like materials; and Cubic boron nitride.

Journal ArticleDOI
TL;DR: In this paper, the relationship between phonon Raman spectra and structure was established and illustrated with natural diamond, graphite, carbon, novel brilliants and novel ultrahard substances.

Journal ArticleDOI
TL;DR: In this article, the surface of a diamond epitaxial film was observed to have a reflection high-energy electron diffraction (RHEED) pattern of the 2×1/1×2 structure.
Abstract: Scanning tunneling microscopy (STM) observation was performed for the surface of diamond epitaxial film which was grown on a diamond (001) substrate by microwave plasma-assisted chemical vapor deposition (CVD). The surface was stable even in air, and it showed a reflection high-energy electron diffraction (RHEED) pattern of the 2×1/1×2 structure. Images of the atomic level corresponding to the RHEED pattern were obtained by STM in air. Significant extension of dimer rows was observed over the entire surface. Strong similarity between Si(001) grown by molecular beam epitaxy (MBE) and diamond (001) grown by CVD was shown.

Journal ArticleDOI
01 May 1991
TL;DR: In this article, the status of the emerging technology with an emphasis on the areas of current research activity is reviewed, with a focus on the emerging technologies of semiconductor diamond technology.
Abstract: Electronic applications of semiconductor diamonds are addressed. Doping and electrical properties of these films, formation of low-resistive 'ohmic' contacts, surface modification methods, and experimental device applications are discussed. Of particular interest are high-temperature (300 degrees C) MOSFETs and metal contacts to CVD (chemical vapor deposition) diamond films which were used to fabricate high-temperature (580 degrees C) Schottky diodes, rudimentary MESFETs, and blue light-emitting diodes (LEDs). The status of the emerging technology is reviewed with an emphasis on the areas of current research activity. >

Journal ArticleDOI
16 Aug 1991-Science
TL;DR: Two modified forms of carbon were quenched by a rapid-cooling technique from graphite sheets shock-compressed to 65 gigapascals and 3700 K, and the n-diamond, obtained from the most rapidly cooled part, has a crystal structure close to that of cubic diamond.
Abstract: Two modified forms of carbon were quenched by a rapid-cooling technique from graphite sheets shock-compressed to 65 gigapascals and 3700 K. One form, ``n-diamond," which was obtained from the most rapidly cooled part, has a crystal structure close to that of cubic diamond. The other form, found in the relatively slow-cooled part, was comparable to an i-carbon prepared by an ion-beam technique. The n-diamond is interpreted as a metastable form, the same as hexagonal diamond, converted from graphite through a martensitic transition, for which either the region or the path may be different from that of hexagonal diamond. The second form was found to be produced through reconstruction.

Journal ArticleDOI
TL;DR: In this paper, the authors simulated MOSFETs with channel lengths smaller than 0.25 mu m with substrates of four different semiconductors and one alloy of the diamond and zinc-blende structures (n-channel Ge, Si, GaAs, InP, In/sub 0.53/Ga/sub 1.47/As, and p-channel Si) with a selfconsistent two-dimensional Monte Carlo program.
Abstract: For pt.I see ibid., vol.38, no.3, p.634-49, March 1991. MOSFETs with channel lengths smaller than 0.25 mu m with substrates of four different semiconductors and one alloy of the diamond and zinc-blende structures (n-channel Ge, Si, GaAs, InP, In/sub 0.53/Ga/sub 0.47/As, and p-channel Si) were simulated at 77 and 300 K with a self-consistent two-dimensional Monte Carlo program. With the exception of the In-based materials, the speed of the devices appears to be largely independent of the semiconductor. This universal behavior results from the similarity among the medium-energy-scale features of the band structures of the cubic semiconductors. Low-energy concepts, such as mobility and effective mass, fail to describe charge transport as carriers populate a larger fraction of the Brillouin zone in these small devices driven at reasonably high biases. The assumptions made, the approximations used, and, in particular, the meaning of the words speed and reasonably mentioned above are discussed. >

Journal ArticleDOI
TL;DR: The optical properties of diamond are examined in the energy region up to 25 eV using a modified parabolic-band model to explain existing experimental data on the dispersion of the real and imaginary part of the dielectric function.
Abstract: The optical properties of diamond are examined in the energy region up to 25 eV. A modified parabolic-band model is used to explain existing experimental data on the dispersion of the real and imaginary part of the dielectric function. Optical properties such as reflectance, index of refraction, and extinction coefficient are also determined in the same region.

Journal ArticleDOI
19 Apr 1991-Science
TL;DR: A laser method based upon carbon ion implantation and pulsed laser melting of copper has been used to produce continuous diamond thin film, which confirmed the films to be defect-free single crystal over large areas of up to several square micrometers with no grain boundaries.
Abstract: A laser method based upon carbon ion implantation and pulsed laser melting of copper has been used to produce continuous diamond thin film. Carbon ions were implanted with ion energies in the range of 60 to 120 keV, and doses of 1.0 x 1018 to 2.0 x 1018 ions cm–2. The ion-implanted specimens were treated with nanosecond excimer laser pulses with the following parameters: energy density, 3.0 to 5.0 J cm–2; wavelength, 0.308 µm; pulse width, 45 nanoseconds. The specimens were characterized with scanning electron microscopy (SEM), x-ray diffraction, Rutherford backscattering/ion channeling, Auger, and Raman spectroscopy. The macroscopic Raman spectra contained a strong peak at 1332 cm–1 with full width at half maximum of 5 cm–1, which is very close to the quality of the spectra obtained from single-crystal diamond. The selected area electron diffraction patterns and imaging confirmed the films to be defect-free single crystal over large areas of up to several square micrometers with no grain boundaries. Low voltage SEM imaging of surface features indicated the film to be continuous with presence of growth steps.

Patent
04 Jan 1991
TL;DR: In this article, a method of manufacturing multilayer metal coatings for bonding polycrystalline diamond compacts and diamond crystals to a matrix comprises a first metal layer of a refractory metal, such as tungsten, a compliant metal layer, and an outer metal layer.
Abstract: To prevent thermal stress from damaging a PCD or diamond, multilayer metal coatings for bonding polycrystalline diamond compacts and diamond crystals to a matrix comprise a first metal layer of a refractory metal, such as tungsten, a compliant metal layer of copper, and an outer metal layer of a refractory metal such as tungsten. Metallic bonding layers of a metal, such as nickel, are placed between the tungsten and copper layers for improved bonding. The method of manufacturing multilayer metal coatings comprises applying the inner metal layer by chemical vapor deposition, applying the first bonding layer metal by electrolytic deposition, applying the compliant layer metal by electrolytic deposition, applying the second bonding layer by electrolytic deposition and applying the outer layer by chemical vapor deposition. A superabrasive tool element comprises a coated diamond product bonded either to a matrix comprising tungsten carbide or iron powder or to a cemented tungsten carbide support.

Journal ArticleDOI
TL;DR: In this article, a Raman spectroscopic study of polycrystalline diamond films using a wide range of incident photon energies (1.16 −4.82 eV) was conducted.
Abstract: We report on a Raman spectroscopic study of polycrystalline diamond films using a wide range of incident photon energies (1.16–4.82 eV). The scattering intensity of amorphous sp2‐bonded carbon is found to vary considerably as a function of the incident photon energy as compared to the strength of the 1332 cm−1 Raman line from sp3‐bonded diamond. There is also a frequency downshift of the apparent peak position for scattering from the sp2‐bonded carbon with decreasing photon energy. Excitation in the infrared range is shown to give a high sensitivity to scattering from amorphous sp2‐bonded carbon whereas ultraviolet excitation enhances the 1332 cm−1 signal from crystalline diamond considerably even in nanocrystalline films.

Journal ArticleDOI
01 Jan 1991-Nature
TL;DR: In this article, it was shown that the transformation from graphite to diamond is martensitic for temperatures substantially lower than the melting temperature, and that the phase transition should be fast if shock pressure is applied parallel to the c axis of the graphite crystal structure.
Abstract: ONE important method of diamond synthesis is shock compression of graphite and other forms of carbon to high pressures and temperatures, and subsequent quenching to yield metastable diamond. This process, which occurs in microseconds, happens naturally in the impact of meteors1,2, within products of explosives3,4, and by explosive compression of powders5,6. A major unresolved issue is whether the shock-induced phase transition of graphite to diamond is martensitic or diffusive. The relation between the crystal structures of graphite and hexagonal diamond suggests that the phase transition should be fast and martensitic if shock pressure is applied parallel to the c axis (normal to the basal planes) of the graphite crystal structure. Here we report measurements of shock-wave histories for this transition whichshow that it occurs in ~ 10 ns. These results imply that the transformation from graphite to diamond is martensitic for temperatures substantially lower than the melting temperature. We observe an unexpectedly large sensitivity of kinetics to sample morphology. As well as answering questions concerning the physical nature of the transformation, our results are relevant to optimization of diamond yield in industrial synthetic methods.

Journal ArticleDOI
TL;DR: The combined results permit deduction of reliable fine-structure assignments for three states of the center and accurate values for zero-field intersystem crossing and spin-lattice relaxation rates from linewidthsof individual resonances in the four-wave-mixing spectrum.
Abstract: A new phase-modulation technique for nonlinear laser spectroscopy is applied with a relative resolving power in the sub-Hz range to measure fundamental relaxation processes of the N-V center in diamond. Complementary EPR experiments versus temperature establish the spin character of the ground state in the absence of optical illumination and show that spin-lattice decay occurs via two-phonon processes involving the dominant vibrational mode. The combined results permit deduction of reliable fine-structure assignments for three states of the center and accurate values for zero-field intersystem crossing and spin-lattice relaxation rates from linewidths of individual resonances in the four-wave-mixing spectrum.