Synthesis of Metastable Diamond

1989 ◽  
Vol 162 ◽  
Author(s):  
Thomas R. Anthony
Keyword(s):  
Atomic Hydrogen ◽  
High Pressures ◽  
Metastable Phase ◽  
Equilibrium Phase ◽  
Diamond Surface ◽  
Diamond Growth ◽  
Hydrocarbon Gases ◽  
Carbon Solubility ◽  
Carbon Radicals ◽  
Liquid Metal Solution

ABSTRACTDiamond can be grown as an equilibrium phase from a liquid metal solution containing carbon at high pressures and high temperatures. Diamond can also be grown as a metastable phase at subatmospheric pressures and moderate temperatures from hydrocarbon gases in the presence of atomic hydrogen. Atomic hydrogen serves several critical roles in CVD diamond growth, namely: 1) stabilization of the diamond surface, 2) reduction of the size of the critical nucleus, 3) “dissolution” of carbon in the gas, 4) production of carbon solubility minimum, 5) generation of condensable carbon radicals in the gas, 6) abstraction of hydrogen from hydrocarbons attached to surface, 7) production of vacant surface sites, 8) etching of graphite, 9) suppression of polycycic aromatic hydrocarbons. A search for substitutes for atomic hydrogen have been unsuccessful to date but several new processes that do not use atomic hydrogen are currently under study.

Structure Stability in Plasma Chemistry

1998 ◽  
Vol 544 ◽  
Author(s):  
Ji-Tao Wang ◽  
David Wei Zhang ◽  
Zhi-Jie Liu ◽  
Jian-Yun Zhang ◽  
Shi-Jin Ding ◽  
...  
Keyword(s):  
Metastable Phase ◽  
Equilibrium Phase ◽  
Plasma Chemistry ◽  
Cvd Diamond ◽  
Low Pressure ◽  
Diamond Growth ◽  
Stable Phase ◽  
Structure Stability ◽  
Pressure Equilibrium ◽  
Saturated Structure

AbstractDiamond is a metastable phase, while graphite is a stable phase in low pressure equilibrium phase diagrams of carbon. However, diamond with saturated structure of π bonds is more stable than graphite with unsaturated structure of n bonds during the existence of activated particles generated by plasma. That provides an excellent explanation for the plasma and other activated CVD diamond growth under low pressure taking place with simultaneous graphite etching.

Kinetic Monte Carlo Simulation of Diamond Film Growth with the Inclusion of Surface Migration

1998 ◽  
Vol 527 ◽  
Author(s):  
Armando Netto ◽  
Michael Frenklach
Keyword(s):  
Monte Carlo ◽  
Monte Carlo Simulations ◽  
Film Growth ◽  
Kinetic Monte Carlo ◽  
Diamond Films ◽  
State Theory ◽  
Diamond Surface ◽  
Diamond Growth ◽  
Gaseous Species ◽  
Surface Migration

ABSTRACTDiamond films are of interest in many practical applications but the technology of producing high-quality, low-cost diamond is still lacking. To reach this goal, it is necessary to understand the mechanism underlying diamond deposition. Most reaction models advanced thus far do not consider surface diffusion, but recent theoretical results, founded on quantum-mechanical calculations and localized kinetic analysis, highlight the critical role that surface migration may play in growth of diamond films. In this paper we report a three-dimensional time-dependent Monte Carlo simulations of diamond growth which consider adsorption, desorption, lattice incorporation, and surface migration. The reaction mechanism includes seven gas-surface, four surface migration, and two surface-only reaction steps. The reaction probabilities are founded on the results of quantum-chemical and transition-state-theory calculations. The kinetic Monte Carlo simulations show that, starting with an ideal {100}-(2×1) reconstructed diamond surface, the model is able to produce a continuous film growth. The smoothness of the growing film and the developing morphology are shown to be influenced by rate parameter values and by deposition conditions such as temperature and gaseous species concentrations.

Molecular Dynamic Structure Investigations of the Surface Stability and Adsorption of H, H2, CH3, C2H2: (100) Diamond

1992 ◽  
Vol 270 ◽  
Author(s):  
Th. Frauenheim ◽  
P. Blaudeck ◽  
D. Porezag
Keyword(s):  
Density Functional ◽  
Dynamic Structure ◽  
Md Simulations ◽  
Diamond Surface ◽  
Diamond Growth ◽  
Minimal Basis ◽  
Surface Stability ◽  
Hydrogen Supply ◽  
Reaction Processes ◽  
Structure Investigations

ABSTRACTSurface properties - stability and reconstruction - of clean and hydrogenated diamond (100) have been studied by real temperature molecular dynarnic (MD) simulations using an approximate density functional (DF) theory expanding the total electronic wave function in a minimal basis of localized atomic valence electron orbitals (LCAO - ansatz). The clean surface is highly unstable against a spontaneous dimerization resulting in a 2×1 reconstruction. Atomic hydrogen in the gas phase above the top surface at all temperatures and H2 molecules approaching the center of the dimer bond at room temperature are reactive in breaking the dimer π-bonds forming a monohydrogenated surface which maintains a stable 2×1 structure but with elongated surface C-C dimer bonds remaining stable against continuing hydrogen supply. The dihydrogenated surface taking a 1×1 structure, because of steric overcrowding dynamically becomes unstable against forming a 1×1 (alternating) di-, monohydrogenated surface. As first elementary reaction processes which may be discussed in relation to diamond growth we studied the thermal adsorption of CH3 and C2H2 onto a clean 2×l reconstructed (100) diamond surface.

Metastable Phase Equilibria in Co-Deposited Ni1−xZrx Thin Films

1991 ◽  
Vol 230 ◽  
Author(s):  
J. B. Rubin ◽  
R. B. Schwarz
Keyword(s):  
Thin Films ◽  
Cooling Rate ◽  
Metastable Phase ◽  
Equilibrium Phase ◽  
Equilibrium Phase Diagram ◽  
Amorphous Structure ◽  
Nucleation Theory ◽  
Glass Forming ◽  
Constant Heating

AbstractWe determine the glass forming range (GFR) of co-deposited Ni1−xZrx (0 < x < 1) thin films by measuring their electrical resistance during in situ constant-heating-rate anneals. The measured GFR is continuous for 0.10 < x < 0.87. We calculate the GFR of Ni-Zr melts as a function of composition and cooling rate using homogeneous nucleation theory and a published CALPHAD-type thermodynamic modeling of the equilibrium phase diagram. Assuming that the main competition to the retention of the amorphous structure during the cooling of the liquid comes from the partitionless crystallization of the terminal solid solutions, we calculate that for dT/dt = 1012 K s−1, the GFR extends to x = 0.05 and x = 0.96. Better agreement with the measured values is obtained assuming a lower ‘effective’ cooling rate during the condensation of the films.

Apparatus for low-temperature growth of diamond-containing films

1989 ◽  
Vol 4 (5) ◽  
pp. 1243-1245 ◽  
Author(s):  
P. H. Fang ◽  
J. H. Kinnier
Keyword(s):  
Substrate Temperature ◽  
Electronic Devices ◽  
Silicon Crystal ◽  
Discharge Voltage ◽  
Diamond Growth ◽  
Diamond Like Carbon ◽  
Hydrocarbon Gases ◽  
Temperature Growth ◽  
Hot Filament ◽  
Deposited Film

In current processes of diamond growth, the substrate temperature is in general around 600–900 °C. In the case of diamond-like carbon, the substrate temperature is lower, around 25–200 °C. There are many superior properties of diamond compared with diamond-like carbon; however, the high temperature requirement to grow diamond precludes many technologically important substrate materials such as zinc sulfide for an infrared window or electronic devices on which protective diamond layers are to be coated. The present approach is a hot filament DC glow discharge of hydrocarbon gases. A graphite hot filament cathode is inserted in a discharge cylinder tube anode. The discharge voltage is in the range of 50 to 250 volts at a methane gas pressure of about 100 microns. A negative biased voltage of 100 volts is applied between the cathode and the substrate. A magnetic field of 1 kG is applied near the cathode-anode assembly. At a substrate temperature of 200–400 °C, the deposited film on silicon crystal is confirmed by an electron diffraction pattern to consist of microcrystalline diamond.

A mechanism of CVD diamond film growth deduced from the sequential deposition from sputtered carbon and atomic hydrogen

1994 ◽  
Vol 9 (6) ◽  
pp. 1546-1551 ◽  
Author(s):  
Darin S. Olson ◽  
Michael A. Kelly ◽  
Sanjiv Kapoor ◽  
Stig B. Hagstrom
Keyword(s):  
Growth Mechanism ◽  
Atomic Hydrogen ◽  
Film Growth ◽  
Deposition Process ◽  
Cvd Diamond ◽  
Surface Growth ◽  
Diamond Surface ◽  
Hydrogen Flux ◽  
Sequential Deposition ◽  
Disordered Carbon

We describe a growth mechanism of CVD diamond films consisting of a series of surface reactions. It is derived from experimental observations of a sequential deposition process in which incident carbon flux and atomic hydrogen flux were independently varied. In this sequential process, film growth rate increased with atomic hydrogen exposure, and a saturation in the utilization of carbon was observed. These features are consistent with a surface growth process consisting of the following steps: (i) the carburization of the diamond surface, (ii) the deposition of highly disordered carbon on top of this surface, (iii) the etching of disordered carbon by atomic hydrogen, (iv) the conversion of the carburized diamond surface to diamond at growth sites by atomic hydrogen, and (v) the carburization of newly grown diamond surface. The nature of the growth sites on the diamond surface has not been determined experimentally, and the existence of the carburized surface layer has not been demonstrated experimentally. The surface growth mechanism is the only one consistent with the growth observed in conventional diamond reactors and the sequential reactor, while precluding the necessity of gas phase precursors.

Adsorption of Hydrocarbon Radicals on the Hydrogenated Diamond Surface

1989 ◽  
Vol 162 ◽  
Author(s):  
Mark R. Pederson ◽  
Koblar A. Jackson ◽  
Warren E. Pickett
Keyword(s):  
Carbon Atom ◽  
Bond Length ◽  
Diamond Surface ◽  
Diamond Growth ◽  
Dangling Bond ◽  
Methyl Radical ◽  
Acetylene Molecule ◽  
Bulk Diamond ◽  
Equilibrium Geometries ◽  
Insight Into

ABSTRACTIn order to gain insight into diamond growth, we have calculated equilibrium geometries for several adsorbates on the hydrogenated diamond <111> surface. While the adsorption height of a single methane radical onto a dangling bond is found to be in excellent agreement with the bulk-diamond bond length, the back bonded hydrogens of adjacent adsorbed methyl radicals repel one another. In contrast, adjacent acetlyinic radicals do not repel one another but lead to the introduction of double carbon bonds, misplaced carbon atoms above the active layer and a bond length which is too short in comparison to that of bulk diamond. Our calculations on the acetylene molecule near a dangling bond indicate that the resulting adsorbate bond length is substantially too large and that the carbon atom is unlikely to be stable directly above the surface carbon atom. Of the adsorbates studied, geometrical arguments suggest that the methyl radical is likely to be the most ideal adsorbate.

Design and Analysis of a High Pressure Apparatus

1980 ◽  
Vol 102 (3) ◽  
pp. 633-640
Author(s):  
K. C. Rolle ◽  
J. N. Crisp ◽  
A. N. Palazotto
Keyword(s):  
Finite Element ◽  
High Pressure ◽  
Phase Diagrams ◽  
High Pressures ◽  
Equilibrium Phase ◽  
Original Design ◽  
Piston Displacement ◽  
Crude Analysis ◽  
High Pressure Apparatus

In the determination of equilibrium phase diagrams, i.e., pressure volume-temperature relations for lubricants at pressures up to 2800 MPa and temperatures of 378K, one must carry out a highly sophisticated design of a high pressure apparatus. In 1935 Bridgman designed a piston-displacement device and measured the compressibility of numerous materials at high pressures. However, in order to obtain accurate equilibrium phase diagrams for lubricants, Bridgman’s relatively crude analysis must be considerably refined. The authors have extended this original design using finite element techniques to accurately correct pertinent measurements which are in turn incorporated into the expressions used in determining the pressure-volume temperature relations of lubricants.

In-Situ Diagnostics of Diamond CVD

1988 ◽  
Vol 131 ◽  
Author(s):  
J. E. Butler ◽  
F. G. Celii ◽  
P. E. Pehrsson ◽  
H. -t. Wang ◽  
H. H. Nelson
Keyword(s):  
Chemical Vapor ◽  
Diamond Surface ◽  
Diamond Growth ◽  
Chemical Vapor Deposition Growth ◽  
Laser Absorption ◽  
Species Formation ◽  
Photon Ionization ◽  
Diode Laser Absorption

ABSTRACTThe deposition of diamond, a metastable crystalline form of carbon, from low pressure gases poses intriguing questions about the mechanisms of growth. Tunable IR Diode Laser Absorption Spectroscopy, Laser Multi-Photon Ionization Spectroscopy, and Laser Induced Fluorescence were used to characterize the gaseous environment in the Chemical Vapor Deposition growth of diamond films. The quality of the deposited material was examined by optical and SEM microscopies, and Raman, Auger, and XPS spectroscopies. When a reactant mixture of 0.5% methane in hydrogen, was passed across a hot Tungsten filament (2000 C), C2H2, C2H4, H and CH3 were detected above the growing diamond surface, and concentration limits for undetected species were determined. These results are discussed in terms of simple models for species formation and consumption, as well as the implications for the diamond growth mechanism.

Metastable Phase Equilibria in the Aqueous Ternary System Containing Potassium, Lithium and Chloride Ions at 298.15 K

2011 ◽  
Vol 233-235 ◽  
pp. 1619-1622 ◽  
Author(s):  
Ying Zeng ◽  
Xu Dong Yu ◽  
Jing Qiang Zhang ◽  
Long Gang Li
Keyword(s):  
Phase Diagram ◽  
Ternary System ◽  
Solid Phase ◽  
Metastable Phase ◽  
Equilibrium Phase ◽  
Chloride Ions ◽  
Crystallization Field ◽  
Metastable Equilibrium ◽  
Eutectic Type ◽  
Salting Out

The metastable phase equilibrium in the ternary system containing potassium, lithium and chloride ions was studied at 298.15 K using an isothermal evaporation method. The solubility, density and refractive index of the equilibrated solution were measured. The crystalloid forms of the solid phase were determined using a schreinermarks wet residue method. On the basis of the experimental data, the metastable equilibrium phase diagram and the physicochemical properties vs composition in the ternary system at 298.15 K were plotted. The experimental results show that this system is of a simple eutectic type system, no double salt or solid solution formed at 298.15 K. The phase diagram consists of one invariant point, two uninvariant curves, and two crystallization regions. The crystallization regions correspond to potassium chloride (KCl) and lithium chloride monohydrate (LiCl·H2O), respectively. Salt KCl has the largest crystallization field, whereas salt LiCl·H2O has the smallest crystallization field. Salt LiCl has strong salting-out effect on salt KCl.

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