Showing papers on "Diamond published in 1999"
TL;DR: The recent development in the field of superhard materials with Vickers hardness of ⩾40 GPa is reviewed in this article, where two basic approaches are outlined including the intrinsic superhard material, such as diamond, cubic boron nitride, C3N4, carbonitrides, etc. and extrinsic, nanostructured materials for which superhardness is achieved by an appropriate design of their microstructure.
Abstract: The recent development in the field of superhard materials with Vickers hardness of ⩾40 GPa is reviewed. Two basic approaches are outlined including the intrinsic superhard materials, such as diamond, cubic boron nitride, C3N4, carbonitrides, etc. and extrinsic, nanostructured materials for which superhardness is achieved by an appropriate design of their microstructure. The theoretically predicted high hardness of C3N4 has not been experimentally documented so far. Ceramics made of cubic boron nitride prepared at high pressure and temperature find many applications whereas thin films prepared by activated deposition from the gas phase are still in the stage of fundamental development. The greatest progress has been achieved in the field of nanostructured materials including superlattices and nanocomposites where superhardness of ⩾50 GPa was reported for several systems. More recently, nc-TiN/SiNx nanocomposites with hardness of 105 GPa were prepared, reaching the hardness of diamond. The principles of de...
1,122 citations
TL;DR: In this article, a review of the basic mechanisms of radiation effects in solids with particular emphasis on atom displacements by knock-on collisions is discussed. But the main part of this review deals with alterations of carbon nanostructures by the electron beam in an electron microscope.
Abstract: The paper reviews the principles of interaction of energetic particles with solid carbon and carbon nanostructures. The reader is first introduced to the basic mechanisms of radiation effects in solids with particular emphasis on atom displacements by knock-on collisions. The influence of various parameters on the displacement cross sections of carbon atoms is discussed. The types of irradiation-induced defects and their migration are described as well as ordering phenomena which are observable under the non-equilibrium conditions of irradiation. The main part of this review deals with alterations of carbon nanostructures by the electron beam in an electron microscope. This type of experiment is of paramount importance because it allows in situ observation of dynamic processes on an atomic scale. In the second part, radiation effects in the modifications of elemental carbon, in particular in graphite which forms the crystallographic basis of most carbon nanostructures, are treated in detail. It follows a review of the available experimental results on radiation defects in carbon nanostructures such as fullerenes, nanotubes and carbon onions. Finally, the phenomena of structure formation under irradiation, in particular the self-assembling of spherical carbon onions and the irradiation-induced transformation of graphitic nanoparticles into diamond, are presented and discussed qualitatively in the context of non-equilibrium structure formation.
1,000 citations
TL;DR: In this paper, the synthesis of nanocrystalline diamond films from carbon-containing noble gas plasmas is described, which is the result of new growth and nucleation mechanisms, which involve the insertion of C2, carbon dimer, into carbon-carbon and carbon-hydrogen bonds, resulting in hetereogeneous nucleation rates on the order 1010 cm−2 s−1.
Abstract: ▪ Abstract The synthesis of nanocrystalline diamond films from carbon-containing noble gas plasmas is described. The nanocrystallinity is the result of new growth and nucleation mechanisms, which involve the insertion of C2, carbon dimer, into carbon-carbon and carbon-hydrogen bonds, resulting in hetereogeneous nucleation rates on the order 1010 cm−2 s−1. Extensive characterization studies led to the conclusion that phase-pure diamond is produced with a microstructure consisting of randomly oriented 3–15-nm crystallites. By adjusting the noble gas/hydrogen ratio in the gas mixture, a continuous transition from micro- to nanocrystallinity is achieved. Up to 10% of the total carbon in the nanocrystalline films is located at 2 to 4 atom-wide grain boundaries. Because the grain boundary carbon is π-bonded, the mechanical, electrical, and optical properties of nanocrystalline diamond are profoundly altered. Nanocrystalline diamond films are unique new materials with applications in fields as diverse as tribolo...
858 citations
809 citations
TL;DR: A detailed assessment of the current status of diamond-like carbon (DLC) film deposition is given in this article, where the authors discuss deposition systems, characterization methods, film properties and possible applications.
497 citations
TL;DR: A review of the methods used, and the results obtained, by a variety of groups in their attempts to prepare carbon nitride films is presented in this paper, with a somewhat speculative set of conclusions.
391 citations
TL;DR: In this article, the chemical, mechanical and tribological properties of the diamond-like carbon (DLC) coatings are discussed and a review of recent developments in the chemical and mechanical characterization of the ultra-thin coatings is presented.
316 citations
TL;DR: The present results indicate that diamond is a useful electrode material for the analytical detection of NADH, making it attractive for use in sensors based on enzyme-catalyzed reactions involving NADH as a cofactor.
Abstract: Conductive boron-doped chemical vapor-deposited diamond thin films, already known to have superior properties for general electroanalysis, including low background current and a wide potential window, are here shown to have additional advantages with respect to electrochemical oxidation of nicotinamide adenine dinucleotide (NADH), including high resistance to deactivation and insensitivity to dissolved oxygen. Cyclic voltammetry, amperometry, and the rotating disk electrode technique were used to study the reaction in neutral pH solution. Highly reproducible cyclic voltammograms for NADH oxidation were obtained at as-deposited diamond electrodes. The response was stable over several months of storage in ambient air, in contrast to glassy carbon electrodes, which deactivated within 1 h. The diamond electrode exhibited very high sensitivity for NADH, with an amperometric detection limit of 10 nM (S/N = 7). The response remained stable, even in the very low concentration range, for several months. In additio...
237 citations
Book•
01 Aug 1999
TL;DR: The Heat of the Night and the Dust of the Battlefield Optical Properties of Infrared Windows Optical Performance of IR Windows Mechanical Properties Thermal Properties Fabrication of IR Materials Optical Coatings Erosion and Erosions Protection Proof Testing Diamond - Materials for the Future Appendices as mentioned in this paper.
Abstract: The Heat of the Night and the Dust of the Battlefield Optical Properties of Infrared Windows Optical Performance of Infrared Windows Mechanical Properties Thermal Properties Fabrication of Infrared Materials Optical Coatings Erosion and Erosion Protection Proof Testing Diamond - Materials for the Future Appendices.
230 citations
TL;DR: Oxygen-terminated diamond electrodes were prepared by exposing as-grown diamond thin films to oxygen plasma, and the apparent surface conductivity was not significantly changed after the oxygen plasma treatment as mentioned in this paper.
229 citations
TL;DR: In this paper, it was shown that diamond can crystallize in alkaline carbonate-fluid melts at pressures and temperatures that correspond to those of natural diamond formation, at a temperature of more than 1,600 °C.
Abstract: Analysis of inclusions1 has shown that natural diamond forms at pressures of 5-6 GPa and temperatures in the range 900-1,400 °C. In non-metallic systems2,4, diamond has been synthesized only at pressures greater than 7 GPa and temperatures of more than 1,600 °C. We find that diamond can crystallize in alkaline carbonate-fluid melts at pressures and temperatures that correspond to those of natural diamond formation.
TL;DR: In this article, a novel mechanism of nano-plasticity of carbon nanotubes under uniaxial compression is observed in which bonding geometry collapses from a graphitic (sp(sup 2)) to a localized diamond-like reconstruction.
Abstract: Nano-plasticity of thin single-wall carbon nanotubes under uniaxial compression is investigated through generalized tight-binding molecular dynamics (GTBMD) and ab-initio electronic structure methods. A novel mechanism of nano-plasticity of carbon nanotubes under uniaxial compression is observed in which bonding geometry collapses from a graphitic (sp(sup 2)) to a localized diamond like (sp(sup 3)) reconstruction. The computed critical stress (approximately equals 153 G Pa) and the shape of the resulting plastic deformation is in good agreement with recent experimental observation of collapse and fracture of compressed carbon nanotubes in polymer composites.
TL;DR: In this article, a review of low-pressure growth methods of diamond films is presented, focusing on recent advances in the understanding of the mechanism of diamond nucleation and metastable growth, which raises hope that single crystalline diamond films are not far beyond reach.
Abstract: In the last decade, we have seen rapid developments in metastable diamond synthesis by means of low-pressure chemical vapor deposition. Concurrently, a fast growing interest in diamond technology has emerged. This review discusses the various low-pressure growth methods of diamond films. Particular attention is paid to recent advances in the understanding of the mechanism of diamond nucleation and metastable growth. These advances are discussed in connection with the advances in diamond heteroepitaxy, which raises hopes that single crystalline diamond films are not far beyond reach. Modern surface science techniques applied to diamond study have played an essential role in these achievements and their contributions are discussed.
TL;DR: In this paper, a geometrically nonlinear theory of martensitic transformations is used to study the cubic to monoclinic transition in the technologically important Ti-Ni shape memory alloys.
TL;DR: The average crystallite size, d, in the range of about 3-8nm determined from XRD by means of the Scherrer formula and integral width of the Bragg peaks compares well with that determined from the Warren-Averbach analysis as discussed by the authors.
Abstract: The average crystallite size, d, in the range of about 3–8 nm determined from XRD by means of the Scherrer formula and integral width of the Bragg peaks compares well with that determined from the Warren–Averbach analysis. TiN films show (200) texture which changes to random orientation of the crystallites when the silicon content reaches about 10 at.%. The biaxial stress of ≤0.4 GPa for ≤10 μm thick films is fairly low. The random stress determined from the Warren–Averbach analysis increases with decreasing crystallite size from about 1 GPa for d ≥10 nm to almost 10 GPa for d≈3 nm. A strong increase is observed for the stability of the nanostructure and of the hardness upon annealing: the recrystallization temperature increases from about 850°C for d≥5 nm to ≥1150°C for d≤3 nm. This is explained by thermodynamical stabilization of the grain boundaries due to segregation. Superhardness remains constant up to recrystallization. For superhardness of about 100 GPa, the elastic modulus of 70–500 GPa and the universal hardness of about 17–22 GPa (loads between 30 and 100 mN) compare well with the hardness of a single-phase nanocrystalline diamond. Besides this extremely high hardness, the coatings also have a very high toughness and elastic recovery of 80–90%.
TL;DR: In this paper, it was argued that the facile electron field emission from carbon systems occurs primarily because surface groups such as C-H can produce large changes in local electron affinity, so that electric fields from the anode can be focused toward unhydrogenated surface areas of high affinity, the fields ending on negative charges in an underlying depletion layer.
Abstract: It is argued that the facile electron field emission from carbon systems occurs primarily because surface groups such as C–H can produce large changes in local electron affinity, so that electric fields from the anode can be focused toward unhydrogenated surface areas of high affinity, the fields ending on negative charges in an underlying depletion layer. The resulting downward band bending creates large surface fields which allow Fowler–Nordheim emission, while not exceeding the material’s breakdown field.
TL;DR: X-ray powder diffraction patterns were simulated for five structures proposed for C3N4, i.e., β-, α-, defect zincblend-type and cubic C 3N4 as discussed by the authors.
TL;DR: In this paper, the basic electrochemical properties of high quality diamond thin-films (3-6μm thick) are highlighted, and the use of diamond for the voltammetric detection of trace metal ions is also illustrated.
TL;DR: In this article, a model describing the structure of diamond nanoclusters produced by explosive shocks is proposed, based on experimental data obtained from x-ray diffraction and small-angle xray scattering.
Abstract: A model describing the structure of diamond nanoclusters produced by explosive shocks is proposed. The model is based on experimental data obtained from x-ray diffraction and small-angle x-ray scattering. This model considers the diamond nanocluster as a crystalline diamond core coated by a carbon shell having a fractal structure. The shell structure depends both on the cooling kinetics of the detonation products and on the method used to extract from them the diamond fraction.
TL;DR: In this article, a 3D periodic nanowriting on diamond clusters is reported, and the periodicity of these corrugated two-dimensional and 3D structures is shorter than that of the laser wavelength used (248 nm for the excimer fs laser and 825 nm for Ti-sapphire fs laser).
Abstract: Three-dimensional (3D), periodic nanowriting on diamond clusters is reported in this letter. Concentric circular rings were observed on diamond microclusters, nucleated near the periphery of a laser-irradiated region, when chemical-vapor deposited diamond was processed in air, with laser pulses of 380 fs duration and at a wavelength of 248 nm. Periodic ripples also have been observed on single-crystal and polycrystalline diamond surfaces. Further, it is experimentally shown that the periodicity of these corrugated two-dimensional and 3D structures is shorter than that of the laser wavelength used (248 nm for the excimer fs laser and 825 nm for the Ti–sapphire fs laser).
TL;DR: Experiments using laser-heated diamond anvil cells show that methane (CH4) breaks down to form diamond at pressures between 10 and 50 gigapascals and temperatures of about 2000 to 3000 kelvin, in agreement with theoretical predictions.
Abstract: Experiments using laser-heated diamond anvil cells show that methane (CH4) breaks down to form diamond at pressures between 10 and 50 gigapascals and temperatures of about 2000 to 3000 kelvin. Infrared absorption and Raman spectroscopy, along with x-ray diffraction, indicate the presence of polymeric hydrocarbons in addition to the diamond, which is in agreement with theoretical predictions. Dissociation of CH4 at high pressures and temperatures can influence the energy budgets of planets containing substantial amounts of CH4, water, and ammonia, such as Uranus and Neptune.
TL;DR: In this article, the three omega thermal conductivity measurement method is analyzed for the case of one or more thin films on a substrate of finite thickness, and the analysis is used to obtain the thermal conductivities of SiO2 films on Si substrates and of a chemical vapor deposition (CVD) diamond plate.
Abstract: The three omega thermal conductivity measurement method is analyzed for the case of one or more thin films on a substrate of finite thickness. The analysis is used to obtain the thermal conductivities of SiO2 films on Si substrates and of a chemical vapor deposition (CVD) diamond plate. For the case of the SiO2 films on a Si, we find an apparent thickness dependence of the thermal conductivity of the SiO2 films. However, the data can also be explained by a thickness-independent thermal conductivity and an interfacial thermal resistance. For the case of the CVD diamond plate, the fit of the theory to the experimental data is significantly improved if we assume that an interface layer separates the heater from the diamond plate.
TL;DR: In this article, a review of polishing and planarization techniques for polycrystalline chemically vapor-deposited (CVD) diamond films and substrates is presented.
TL;DR: Many diamonds are natural antiques that formed in presolar supernovae by carbon vapor deposition, in asteroidal impacts and meteorite craters by shock metamorphism, and in Earth's mantle 1 to 2 billion years after planetary accretion from fluids and melts.
Abstract: Diamond is a remarkable mineral and has been long recognized for its unusual physical and chemical properties: robust and widespread in industry, yet regally adorned. This diversity is even greater than formally appreciated because diamond is recognized as an extraordinary recorder of astrophysical and geodynamic events that extend from the far reaches of space to Earth's deep interior. Many diamonds are natural antiques that formed in presolar supernovae by carbon vapor deposition, in asteroidal impacts and meteorite craters by shock metamorphism, and in Earth's mantle 1 to 2 billion years after planetary accretion from fluids and melts. The carbon in diamond is primordial, but there are unexplained isotopic fractionations and uncertainties in heterogeneity.
DSM1
TL;DR: The first unambiguous evidence of the presence of small crystallites of diamond in the dusty envelopes surrounding stars was reported in this paper, where two infrared emission bands at 3.43 and 3.53 μm were identified as the vibrational modes of hydrogen-terminated crystalline facets of diamond.
Abstract: Since the discovery of small diamond grains in meteorites, the presence of such grains in the interstellar medium has been suspected. Here we report what we think to be the first unambiguous evidence of the presence of small crystallites of diamond in the dusty envelopes surrounding stars. Thanks to experimental results obtained in different laboratories on the diamond growth process, we identify two peculiar unidentified infrared emission bands at 3.43 and 3.53 μm as the vibrational modes of hydrogen-terminated crystalline facets of diamond. The intensities of these two strong features observed in the envelope of HD 97048 correspond to a mass of 10-10 to 10-9 M☉ of diamond dust at an equilibrium temperature of ~1000 K.
TL;DR: In this paper, the friction and wear properties of nanocrystalline diamond (NCD) films grown in Afullerene (C{sub 60}) and Ar-CH{sub 4} microwave plasmas were investigated.
Abstract: 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.
TL;DR: In this article, the authors used a standard semi-empirical method (MNDO) to explain the preferential exfoliation of {111} planes over other low index diamond planes.
Abstract: In recent high resolution transmission electron microscopic studies we have found that high temperature vacuum annealing (1200–1800 K) of ultradispersed (2–5 nm) and micron size diamond produces fullerene-like graphitic species, namely, onion-like carbon and closed curved graphite structures (multilayer nanotubes and nanofolds), respectively. Here we undertake theoretical studies to help in the understanding of the experimental data for these systems. (1) Calculations of cluster models by a standard semiempirical method (MNDO a software package) are used to explain the preferential exfoliation of {111} planes over other low index diamond planes. (2) The same approach suggests the likelihood that the graphitization is initiated by a significant thermal displacement of a single carbon atom at temperatures close to the Debye temperature. (3) At the diamond–graphite interface we have observed the formation of two curved graphitic sheets from three diamond {111} planes. We suggest that the evolution of this in...
TL;DR: In this article, the Raman micro-spectroscopy of hardness indentations was used to investigate contact-induced phase transformations in hard and brittle materials including semiconductors (Si, Ge, GaAs and InSb), and common ceramic materials such as SiC and SiO2 (α-quartz and silica glass).
Abstract: During hardness indentation, materials are subjected to highly l highly localized stresses. These stresses not only cause crack formation and plastic deformation by dislocation gliding, but a complete change of the crystal structure and formation of amorphous phases or high-pressure polymorphs can occur in the zone of maximum contact stresses. Such contact-induced phase transformations were observed in hard and brittle materials including semiconductors (Si, Ge, GaAs and InSb) and common ceramic materials such as SiC and SiO2 (α-quartz and silica glass). A prime tool for their investigation is the Raman microspectroscopy of hardness indentations.
In Si and Ge, there is an initial transformation to metallic high-pressure phases upon hardness indentation and a subsequent formation of crystalline, nanocrystalline, or amorphous phases depending on the conditions of the hardness test, in particular the unloading rate. A phase transformation occurs also in InSb, whereas the results for GaAs do not give sufficient evidence for phase transformations. Indentation-induced amorphization has been observed in SiC and quartz. Even diamond has been shown to undergo amorphization and phase transformation under nonhydrostatic stress conditions imposed by indentation tests. Copyright © 1999 John Wiley & Sons, Ltd.
TL;DR: In this paper, the authors used micro-Raman spectroscopy to determine what happens to diamond when it is subjected to high contact compression as a result of pressing a sharp diamond indenter against its surface.
Abstract: Despite almost forty years of trying, no one has managed to transform diamond into graphite under pressure1, or find out what the pressure limit for diamond might be2. If diamond were to behave like other group IV elements, such as silicon, germanium or tin, it would transform under compressive indentation to the β-tin structure3, but it does not2,4. Here we use micro-Raman spectroscopy to determine what happens to diamond when it is subjected to high contact compression as a result of pressing a sharp diamond indenter against its surface4. We find that, under this non-hydrostatic compression, diamond at the point of indentation is transformed into disordered graphite. This discovery may eventually lead to the more efficient machining of diamond.
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TL;DR: In this article, the current status of diamond doping and the electronic properties of the doped layers are described, and some potential applications of doped semiconducting diamond are described.