Showing papers on "Diamond published in 1987"
TL;DR: In this paper, it was shown that part of all of the C-delta is primary, not shock-produced, diamond formed by stellar condensation as a metastable phase.
Abstract: Primitive meteorites contain up to 400 ppm of a very fine-grained type of carbon tentatively called C-delta. Evidence is presented here that part of all of the C-delta is primary, not shock-produced, diamond formed by stellar condensation as a metastable phase. It appears that interstellar dust contains diamond.
640 citations
TL;DR: In this paper, an analysis based on elastic-plastic identation theory has been developed that allows both the prediction of the hardness of a given coating-substrate system and the estimation of shear strains developed at the substrate interface which, for weakly adhered films, leads to delamination of the coating around an indentation.
506 citations
310 citations
TL;DR: In this article, the authors used a cross of double wires with an attached diamond stylus as a force sensor, and demonstrated the potential of atomic force microscopy (AFM) for studying both conducting and nonconducting surfaces.
Abstract: Images of graphite surfaces that are covered with oil reveal the hexagonal rings of carbon atoms. Images of a sodium chloride surface, protected from moisture by oil, exhibit a monoatomic step. Together, these images demonstrate the potential of atomic force microscopy (AFM) for studying both conducting and nonconducting surfaces, even surfaces covered with liquids. Our AFM uses a cross of double wires with an attached diamond stylus as a force sensor. The force constant is ≊40 N/m. The resonant frequency is ≊3 kHz. The lateral and vertical resolutions are 0.15 nm and 5 pm.
274 citations
TL;DR: In this paper, a diamond thin film has been formed by dc plasma chemical vapor deposition with a high growth rate (∼20 μm/h) without surface scratching by diamond or c-BN powder.
Abstract: Diamond thin films have been formed by dc plasma chemical vapor deposition with a high growth rate (∼20 μm/h). The diamond has been grown from methane (CH4) and hydrogen (H2) mixed gases on Si and α‐Al2O3 substrates at a pressure of 200 Torr without surface scratching by diamond or c‐BN powder. The obtained films have good crystallinity in the sense of electron and x‐ray diffraction. Vicker’s hardness of the film is the same as that of natural diamond (∼10 000 kg/mm2). The influence of the dc discharge in a low vacuum (∼200 Torr) on diamond synthesis will be discussed briefly.
244 citations
TL;DR: In this paper, the photoelectrochemical behavior of an electrode made of synthetic diamond has been studied for the first time and the photocurrent, differential capacity and dark current vs. potential curves have been measured on semiconductor diamond polycrystalline films on a tungsten substrate in contact with aqueous electrolyte solutions.
243 citations
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TL;DR: In this paper, a method for removing a single atomic layer from the surface of a crystalline diamond is presented. But the method is not suitable for the removal of a single layer from a diamond.
Abstract: An apparatus, and method therefor, for removing a single atomic layer fromhe surface of a crystalline diamond. In a preferred embodiment, the apparatus comprises: a first delivery system for flooding the surface of the diamond with a pulse of nitrogen dioxide during a first phase of operation to cause a monolayer of nitrogen oxide to be adsorbed to the surface of the diamond; and a second delivery system for impacting the surface of the diamond with a pulse of ions of mixed noble and hydrogen gasses during a second phase of operation in order to remove a single atomic layer from the surface of the diamond. In a preferred method for removing a single atomic layer from the surface of a crystalline diamond, the method comprises the steps of: flooding the diamond surface with a pulse of nitrogen dioxide during the first phase of operation; and impacting the diamond surface with a pulse of ions of mixed noble and hydrogen gasses during a second phase of operation in order to remove a single atomic layer from the surface of the diamond.
213 citations
TL;DR: In this article, point contact transistors and Schottky diodes have been formed on synthetic boron-doped diamond and the first report of diamond transistors that have power gain was made.
Abstract: Point-contact transistors and Schottky diodes have been formed on synthetic boron-doped diamond. This is the first report of diamond transistors that have power gain. Further, the transistors exhibited power gain at 510°C and the Schottky diodes were operational at 700°C.
208 citations
TL;DR: In this paper, microcrystals and microcrystalline films of diamond were prepared on molybdenum substrates in a thermal plasma which was produced by rf inductive heating in an argonhydrogenmethane mixture gas under 1 atm pressure.
Abstract: Microcrystals and microcrystalline films of diamond were prepared on molybdenum substrates in a thermal plasma which was produced by rf inductive heating in an argon‐hydrogen‐methane mixture gas under 1 atm pressure. The deposition rate amounted to 1 μm/min.
199 citations
TL;DR: The internal structure and growth history of diamonds have been investigated by the study of carbon isotopes and the abundance, isotope composition and aggregation state of nitrogen as mentioned in this paper, which suggests that the octahedral diamonds represent a variety of growth events separated in time and space and that the diamonds resided in the lithosphere for a period sufficient for thermal maturation.
196 citations
TL;DR: In this paper, the synthesis of diamond particles in a low pressure plasma has been studied, with emphasis on the investigation of the substrate effect and the plasma conditions, and it was found that a special pre-treatment of silicon substrate made it possible to form dense films, and a thickness of about 15μm could be reached by 20 h discharge.
Abstract: The synthesis of diamond particles in a low pressure plasma has been studied, with emphasis on the investigation of the substrate effect and the plasma conditions. It was found that a special pre-treatment of silicon substrate made it possible to form dense films, and a thickness of about 15μm could be reached by 20 h discharge. Unfortunately, however, the prepared films had poor adhesion. Observations by scanning electron microscope (SEM) showed that the poor adhesion was due to the fact that the film consisted of large particles with a diameter of about 10μm, and each particle had contacted to the substrate only by a point, not by a face. In addition, the plasma diagnostics of optical and ultraviolet emission spectroscopy (OES, 200–750 nm) revealed that CH and H radicals have come to be criteria for the formation of diamonds, and the ratio of radicals drastically affected the characteristics of the deposits. Nucleation and growth mechanism are also discussed.
TL;DR: In this paper, the influence of oxygen on the chemical vapor deposition (CVD) of diamond, gas mixtures of H2-CH4 and H2 -CH4-O2 were used to carry out thermal CVD.
Abstract: In order to investigate the influence of oxygen on the chemical vapor deposition (CVD) of diamond, gas mixtures of H2–CH4 and H2–CH4–O2 were used to carry out thermal CVD. The effects of the oxygen additive were examined by gas chromatography for the exhaust gas and by a characterization of the deposits. With the addition of oxygen, the deposition of graphitic or amorphous carbon could be suppressed, so that the growth rate of diamond increased and the pressure range for the synthesis of diamond was extended. These effects resulted from the fact that the acetylene concentration in a deposition chamber is significantly reduced upon the addition of oxygen.
Patent•
17 Feb 1987TL;DR: In this article, the authors used a thin diamond film made of diamond, which has excellent thermal conductivity, as an insulator film which is formed on a chip immediately below a heat-dissipating bump electrode.
Abstract: A semiconductor device having improved heat-dissipating characteristics employs a thin insulator film made of diamond, which has excellent thermal conductivity, as an insulator film which is formed on a chip immediately below a heat-dissipating bump electrode. Since the thin diamond film has excellent insulating properties and high thermal conductivity, it is possible to improve heat-dissipating characteristics of even a high-power semiconductor device such as a multichip module. In the case of, particularly, a multichip module, the insulation between a mother chip and a child chip can also be ensured by the presence of the thin diamond film.
TL;DR: The sixfold coordinated structures, simple cubic and \ensuremath{\beta}-tin, are found at low pressure to be kinetically unstable, transforming spontaneously, without an energy barrier, into the cubic diamond structure, suggesting that sixfold coordination of liquid carbon will be unlikely to occur at moderate pressure and temperature.
Abstract: The high-pressure properties of carbon in eight different structures are calculated using an ab initio pseudopotential local-orbital method. In particular, the structural properties of hexagonal diamond and variation of its fundamental band gap with pressure are calculated for the first time. The variation of the fundamental gap in hexagonal diamond is found to have the opposite sign to that in cubic diamond, although the cubic and hexagonal forms have almost identical structural properties. Among the structures examined, diamond is found to transform under hydrostatic pressure first to the fourfold coordinated bc-8 (or Si-III) structure. The bc-8 form is favored at pressures greater than 11.1 Mbar. This is a slightly lower transformation pressure than that recently calculated using the pseudopotential plane-wave method. The sixfold coordinated structures, simple cubic and \ensuremath{\beta}-tin, are found at low pressure to be kinetically unstable, transforming spontaneously, without an energy barrier, into the cubic diamond structure. This result suggests that sixfold coordination of liquid carbon will be unlikely to occur at moderate pressure and temperature. Similarly, sixfold coordination is not expected in carbon clusters. A method of fully utilizing crystal symmetry to reduce the amount of computation in evaluating two- and three-center integrals needed in the local-orbital method is developed for the present calculations.
TL;DR: In this article, a short-lived hole burning spectrum has been observed in the 637 nm zero-phonon transition associated with the nitrogen-vacancy centre in diamond.
TL;DR: In this article, the first-derivative of the X-ray excited (XAES) CKLL spectrum from a diamond-like carbon (DLC) film exhibited almost the same spectrum as both the XAES and AES spectra from natural diamond.
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08 Dec 1987
TL;DR: A monolayer diamond tool is made by coating diamond abrasive particles with a carbide-forming metal and then brazing the coated diamond to a tool substrate as discussed by the authors.
Abstract: A monolayer diamond tool is made by coating diamond abrasive particles with a carbide-forming metal and then brazing the coated diamond to a tool substrate.
TL;DR: In this article, a carbon film was deposited by mass-separated negative carbon-ion-beam deposition in the energy range of 25-1000 eV, and the film was optically transparent and served as an electrical insulator.
Abstract: A carbon film was deposited by mass‐separated negative‐carbon‐ion‐beam deposition in the energy range of 25–1000 eV. The carbon film deposited by a C− ion beam was optically transparent (the maximum optical gap was 0.96 eV) and served as an electrical insulator (the maximum electrical resistivity was 1.5×108 Ω cm). The film property strongly depended on the ion‐beam energy for deposition and, the film obtained at the deposition energy of 115–215 eV was the most transparent and the best insulator. Its atomic density was also the highest and was almost the same as that of diamond. The carbon film deposited at room temperature was amorphous and showed no IR absorption. On the other hand, the film deposited at a substrate temperature of 800 °C showed graphitelike rings in reflection high‐energy electron‐diffraction patterns and an IR absorption such as graphite. Its electrical resistivity was much lower. The property of the film deposited by a C−2 ion beam was more strongly dependent on the ion‐beam energy th...
TL;DR: In this paper, a large area chemical vapour deposition of diamond has been obtained using magneto-microwave plasma, where the important point of the developed system is to set the electron cyclotron resonance condition (875 G), where the highest plasma density is expected, at the deposition area by controlling the distribution of an applied magnetic field.
Abstract: Large area chemical vapour deposition of diamond has been obtained using magneto-microwave plasma. The important point of the developed system is to set the electron cyclotron resonance condition (875 G), where the highest plasma density is expected, at the deposition area by controlling the distribution of an applied magnetic field. Even in 10 Torr where complete electron gyrations cannot be expected, the size of the discharge area controlled by the magnetic field is 70-80 mm in diameter. This value is the largest of all plasma deposition systems of diamond. The crystallinity obtained by the above-mentioned plasma compares favourably with those of the best ones by previous methods.
TL;DR: In this paper, the authors used a method coupled with an empirical ionicity scale to predict phase transitions as a function of pressure for all diamond and zinc-blende semiconductors of the form ${A}^{N}$${B}^{8\mathrm{\ensuremath{-}}N}$ where A and B are simple metals or metalloids and N is the number of valence electrons for species A.
Abstract: With the advent of accurate total-energy methods for solids, it has become feasible to determine the relative structural energies of simple solids as a function of pressure. We use such a method coupled with an empirical ionicity scale to predict phase transitions as a function of pressure for all diamond and zinc-blende semiconductors of the form ${A}^{N}$${B}^{8\mathrm{\ensuremath{-}}N}$ where A and B are simple metals or metalloids and N is the number of valence electrons for species A. We find satisfactory agreement between the predicted transition from zinc-blende structure to rocksalt or \ensuremath{\beta}-Sn structures and high-pressure experiments. In addition, we find that changes in ionicity to a large extent control whether the diamond or zinc-blende structure will transform preferentially to rocksalt or to \ensuremath{\beta}-Sn; whereas, for changes in the equilibrium crystal volume, we find the magnitude of the transition pressure changes, but not the structural preference.
Patent•
19 Oct 1987TL;DR: In this article, a method for synthesizing diamond is proposed, which comprises: (a) generating a plasma by electric discharge in a gas selected from the group consisting of a hydrocarbon gas, hydrogen gas, an inert gas and a mixture thereof, decomposing a carbon source by the plasma to form plasma gas containing carbon ions or carbon radicals, and effecting adiabatic expansion of the plasma gas to precipitate diamond.
Abstract: A method for synthesizing diamond, which comprises: (a) generating a plasma by electric discharge in a gas selected from the group consisting of a hydrocarbon gas, hydrogen gas, an inert gas and a mixture thereof, (b) decomposing a carbon source by the plasma to form plasma gas containing carbon ions or carbon radicals, (c) effecting adiabatic expansion of the plasma gas to precipitate diamond.
TL;DR: In this paper, a working definition of diamond-like carbon coatings is proposed, which is similar to the definition of single-crystal diamond-type carbon materials, but with a high degree of sp 3 bonding.
Patent•
24 Jul 1987
TL;DR: In this paper, a bearing for a rotary cone for a rock bit is described, which consists of a multiplicity of small synthetic diamond particles nested within a matrix base, each with an exposed flattened surface to form the bearing.
Abstract: A bearing for a rotary cone for a rock bit is disclosed. The bearing consists of a multiplicity of small synthetic diamond particles nested within a matrix base, each with an exposed flattened surface to form the bearing. The diamond particles are strategically positioned on a bearing surface and secured within the matrix base. A substantially identical synthetic diamond bearing is concentrically positioned adjacent to the first bearing to form the bearing package.
TL;DR: In this article, Hoffmann et al. studied the properties of 3-4-connected honeycombed nets and showed that they have infinite stacks of carbon-carbon double bonds in close contact with each other.
Abstract: A theoretical study of a series of “honeycombed” or ”layered” 3,4-connected nets is presented. The most significant feature of this series of nets is that they have infinite stacks of carbon-carbon double bonds in close contact with each other. Two of these nets have structures that not only contain stacks of 3-connected centers but also have infinite 1-dimensional polymeric units related to cis-polyacetylene. We employ tight-binding band structure calculations on selected examples of these nets to determine their electronic properties. The consequences of a stacked structure are analyzed by calculating the band structure of infinite layers (stacks) of ethylenes. Some of these carbon nets may be metallic. We also show that through-space and through-bond (hyperconjugative) interactions are important in the solid state, but the overall effect of these interactions varies according to the area of k-space that is being sampled. Pursuing our continuing interest in alternative structures of diamond and graphite,’ we decided to study a series of 3,4-connected nets. There are a number of reasons for examining these nets: first, they have an intermediate valency between graphite (3-connected) and diamond (4-connected); second, the density of the nets we will be studying here is intermediate (-3.0 g/cm3) between that of diamond (3.51 g/cm3) and graphite (2.27 g / ~ m ~ ) ; ~ and third, these nets are interesting because they have close intrastack distances (2.3 to 2.8 A) thereby allowing for greater (especially T ) band dispersions (this may make these nets metallic). Before proceeding to a discussion of the electronic properties of these nets we would like to review briefly the current status of the allotropy of carbon. The structurally well-characterized allotropes of carbon are restricted to only two main types: diamond (cubic and hexagonal) and graphite (hexagonal and rh~mbohedra l ) .~ In cubic (1) and hexagonal diamond (2) each carbon atom is tetrahedrally surrounded by four other carbon atoms at a distance of 1.545 A. The structural differences between these two diamond forms can be envisioned in this way: 1 can be imagined to consist of an infinite network of adamantyl moieties, all chair cyclohexane rings, whereas in 2 there are some chair and some boat six-membered T Cornell University. *The Polytechnic. 0002-7863/87/ 1509-6742$01.50/0 rings. Both hexagonal (3) and rhombohedral (4) graphite contain hexagonal carbon layers linked by van der Waals forces. The difference, though, between these two forms lies in the stacking of these sheets. In 3 every third layer repeats (ABAB ...) with the first and second layers displaced away from each other in such a way that one-half of the atoms in each layer are above and below the center of the hexagon in the neighboring layer. 4, on the other hand, has every fourth layer repeating to give an ABCABC ... stacking pattern. There is some evidence for other carbon allotrope^.^ The best studied of these is karbin, sometimes called ~ h a o i t e . ~ . ~ Its structure is thought to contain carbon in alkyne or cumulene needles, 5. Though there has been much work on karbin, our opinion is that (1) Hoffmann, R.; Hughbanks, T.; Kertesz, M.; Bird, P. H. J . Am. Chem. SOC. 1983, 105, 4831. Hoffmann, R.; Eisenstein, 0.; Balaban, A. T. Proc. Nutl. Acad. Sci. U.S.A. 1980, 7 7 , 5588. Balaban, A. T.; Rentia, C. C.; Ciupitu, E. Rev. Roum. Chim. 1968, 13, 231; erratum: Ibid. 1968, 13, 1233. (2) These are theoretical densities calculated from idealized geometries and should be considered as an upper limit to the experimental densities. (3) Donohue, J. The Structure ofthe Elements; Wiley: New York, 1974. (4) S,e the following recent review of experimental and theoretical work: Stankevich, I . V.; Nikerov, M. V.; Bochvar, D. A. Usp. Khim. 1984,53, 1101; Russ. Chem. Reu. 1984, 53, 640. (5) For a review on karbin see: Mel’nichenko, V . M.; Sladkov, A. M.; Nikulin, Yu. N . Usp. Khim. 1982, 51 , 736; Russ. Chem. Reu. 1982, 51, 421. (6) Whittaker, A. G. Science 1978, 200, 763.
TL;DR: In this article, the authors measured noble gases in 17 diamond samples, mostly inclusion free, from diverse, known locations, and found that the noble gases were characterized by a large spread (10^4), ranging from values below atmospheric to close to the solar ratio.
Abstract: We have measured noble gases in 17 diamond samples, mostly inclusion free, from diverse, known locations. The ^3He/^4He ratios are characterized by a large spread (10^4), ranging from values below atmospheric to close to the solar ratio. Highest ratios were seen for an Australian colorless diamond composite and an Arkansas diamond. These samples also have imprecise but intriguing neon isotopic ratios, which are close to the solar value. An origin for the solarlike He and Ne in the diamond samples is unlikely to be accounted for by the presence of nucleogenic or spallogenic components. For single diamond stones a positive correlation is found between ^3He/^4He and ^(13)C/^(12)C, possibly indicating that heavy carbon is accompanied by primordial helium. However, the He result for the Australian colorless diamond composite with low δ^(13)C value requires another explanation, possibly sedimentary carbon contaminated with cosmic dust. The wide variation in ^4He/^(40)_*Ar ratios observed from diamond samples suggests a complex history for the source regions and the diamond crystallization processes. Results for two Australian diamond composites (colorless and colored), which came from the same kimberlite pipe, are especially notable: the colorless stones contain no radiogenic components but solarlike He and Ne isotopic ratios, whereas the colored stones are enriched in radiogenic and fissiogenic components. Seemingly the Australian diamonds crystallized in a heterogeneous environment in the mantle source region. A pair of Arkansas diamonds, believed to be from a single pipe, exhibits similar anomalies.
TL;DR: In this paper, the thermodynamic properties of condensed carbon in the detonation products of TNT have been analyzed with a statistical mechanical model, and it was shown that the heat of formation of diamondlike particles in detonation product is increased by 1-2 kcal/mol (0.04-0.08 eV) relative to that of the graphitic or carbynelike low-pressure phase.
Abstract: The thermodynamic properties of condensed carbon in the detonation products of TNT have been analyzed with a statistical mechanical model. The calculations show that the heat of formation of diamondlike particles in detonation products is increased by 1–2 kcal/mol (0.04–0.08 eV), relative to that of the graphitic or carbynelike low‐pressure phase. The density of the low‐pressure phase also appears to be about 10% higher than that of graphite. The short condensation times of 10−7–10−8 s suggest carbon clusters with a high surface energy. The heat of formation indicates cluster sizes of about 100 A.
Patent•
28 Jun 1987TL;DR: A diamond-coated tungsten carbide base sintered hard alloy material for inserts of cutting tools is presented in this paper, which has greatly improved bond strength or degree of bonding of the diamond coating layer to the matrix and therefore is capable of exhibiting excellent cutting performance over a long period of time.
Abstract: A diamond-coated tungsten carbide-base sintered hard alloy material for inserts of cutting tools, which has greatly improved bond strength or degree of bonding of the diamond coating layer to the matrix and therefore is capable of exhibiting excellent cutting performance over a long period of time. The sintered hard alloy material comprises: (1) a matrix of a sintered hard alloy consisting essentially of 1-4 percent by weight cobalt, and the balance of tungsten carbide and inevitable impurities, the tungsten carbide having a coarse grain structure having an average grain size of 2-10 microns; and (2) a diamond coating layer formed over surfaces of the matrix by forming an etching layer over the matrix surfaces and then forming the diamond coating layer over the matrix surfaces via the etching layer by a low pressure vapor-phase synthesization method. If required, the matrix may further contain CO1-CO8 (ISO) free carbon.
TL;DR: The mechanism of the propagation of the epitaxial growth of diamonds at low pressure was investigated in terms of quantum chemistry in this article, where the most important requirement is the maintaining of positive charges on the growing surface.
Abstract: The mechanism of the propagation of the epitaxial growth of diamonds at low pressure was investigated in terms of quantum chemistry. The reactions for diamond structure formation proceed simultaneously at many points on the surface of a diamond, and the epitaxial growth continues so long as methyl radicals are supplied. The most important requirement is the maintaining of positive charges on the growing surface.
Patent•
14 Feb 1987
TL;DR: In this article, the authors proposed a method to obtain a magnetic recording medium having high mechanical strength, resistance to scratching, good runnability and good wear resistance by forming one kind of protective layer selected from an a-Si layer, amorphous layer contg. Si, polycrystalline layer cont g. Si and diamond-like C film.
Abstract: PURPOSE:To obtain a magnetic recording medium having high mechanical strength, resistance to scratching, good runnability and good wear resistance by forming one kind of protective layer selected from an a-Si layer, amorphous layer contg. Si, polycrystalline layer contg. Si, amorphous C film and diamond- like C film by a plasma CVD method on a magnetic layer. CONSTITUTION:The protective layer consisting of the kind of the layer selected from the a-Si layer, the polycrystalline layer contg. Si, the amorphous C (carbon) film and diamond-like C film or the layer combined with a plural of such layers is formed by the plasma CVD method on the magnetic layer provided on a nonmagnetic base. The thickness of the protective layer is preferably 10-500Angstrom . For example, the layers consisting of muc-SiC, polycrystalline SiC, muc-SiN, polycrystalline SiN, muc-SiO2 and polycrystalline SiO2 are used as the polycrystalline layer contg. Si. a-C:H, a-C:H:F, C film contg. pulverous diamond crystal in the graphite layer, etc. are used for the amorphous C film and diamond-like C film.
TL;DR: In this paper, the friction and wear properties of hard carbon amorphous films with a hot cathode glow discharge in ethylene or methane were examined using a reciprocating tribometer in vacuum and in air.
Abstract: The friction and wear properties of hard carbon films deposited by a hot cathode glow discharge in ethylene or methane were examined by using a reciprocating tribometer in vacuum and in air. A hard carbon film composed of mixed diamond and graphite crystal shows high friction in vacuum. On the other hand, hard carbon amorphous film containing hydrogen shows an extremely low friction coefficient on the order of 0.01 in vacuum.