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.

Studies of Diamond Growth Mechanisms in a Hot Filament Reactor

1989 ◽  
Vol 162 ◽  
Author(s):  
C. Judith Chu ◽  
Benjamin J. Bai ◽  
Mark P. D'Evelyn ◽  
Robert H. Hauge ◽  
John L. Margrave
Keyword(s):  
Growth Process ◽  
Total Concentration ◽  
Cvd Diamond ◽  
Diamond Surface ◽  
Diamond Growth ◽  
Growth Mechanisms ◽  
Methyl Radical ◽  
Hydrocarbon Sources ◽  
Hot Filament ◽  
Heated Filament

ABSTRACTThe incorporation of methane into low-pressure CVD diamond thin films has been compared to that of acetylene. 13CH4 and 12C2 H2 were used as the hydrocarbon sources in a heated-filament CVD diamond growth process at a total concentration of 0.5% hydrocarbon in 99.5% hydrogen. Results indicated that methane and/or methyl radical is the dominant carbon source for diamond growth in a hot filament reactor under steady state conditions and that acetylene is rapidly hydrogenated to methane. Results also indicated that diamond surface reactions play an important role in determining the relative methane to acetylene ratios.

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.

Diamond growth on thin Ti wafers via chemical vapor deposition

1995 ◽  
Vol 10 (11) ◽  
pp. 2685-2688 ◽  
Author(s):  
Qijin Chen ◽  
Zhangda Lin
Keyword(s):  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Titanium Substrate ◽  
Chemical Vapor ◽  
Low Pressure ◽  
Diamond Growth ◽  
X Ray ◽  
Hot Filament ◽  
Insight Into

Diamond film was synthesized on thin Ti wafers (as thin as 40 μm) via hot filament chemical vapor deposition (HFCVD). The hydrogen embrittlement of the titanium substrate and the formation of a thick TiC interlayer were suppressed. A very low pressure (133 Pa) was employed to achieve high-density rapid nucleation and thus to suppress the formation of TiC. Oxygen was added to source gases to lower the growth temperature and therefore to slow down the hydrogenation of the thin Ti substrate. The role of the very low pressure during nucleation is discussed, providing insight into the nucleation mechanism of diamond on a titanium substrate. The as-grown diamond films were characterized by scanning electron microscopy (SEM), Raman spectroscopy, and x-ray analysis.

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.

Interface Defects in n-Type 3C-SiC/SiO2: An EPR Study of Oxidized Porous Silicon Carbide Single Crystals

2005 ◽  
Vol 483-485 ◽  
pp. 273-276 ◽  
Author(s):  
Hans Jürgen von Bardeleben ◽  
J.L. Cantin ◽  
L. Ke ◽  
Y. Shishkin ◽  
Robert P. Devaty ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Carbon Atom ◽  
Spin Hamiltonian ◽  
Dangling Bond ◽  
Interface Defects ◽  
X Band ◽  
Interface Defect ◽  
Bond Center ◽  
Oxidized Porous Silicon ◽  
Hamiltonian Parameters

The defects at the 3C-SiC/SiO2 interface have been studied by X-band EPR spectroscopy in oxidized porous 3C-SiC. One interface defect is detected; its spin Hamiltonian parameters, spin S=1/2, C3V symmetry, g//=2.00238 and g⊥=2.00317, central hyperfine interaction (CHF) with one carbon atom and AB//[001]=48G and superhyperfine (SHF) interaction with three equivalent Si neighbour atoms and TB//[001]=12.4G, allow us to attribute the center to a sp3 coordinated carbon dangling bond center, PbC.

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.

On the optimization of a dc arcjet diamond chemical vapor deposition reactor

1996 ◽  
Vol 11 (3) ◽  
pp. 694-702 ◽  
Author(s):  
S. W. Reeve ◽  
W. A. Weimer ◽  
D. S. Dandy
Keyword(s):  
Growth Rate ◽  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Film Growth ◽  
Chemical Vapor ◽  
Diamond Growth ◽  
Methyl Radical ◽  
Chemical Kinetic Model ◽  
Model Calculations ◽  
Chemical Vapor Deposition Reactor

Based on results from chemical kinetic model calculations, a method to improve diamond film growth in a dc arcjet chemical vapor deposition reactor has been developed. Introducing the carbon source gas (CH4) into an Ar/H2 plasma in close proximity to the substrate produced diamond films exhibiting simultaneous improvements in quality and mass deposition rates. These improvements result from a reduced residence time of the methane in the plasma which inhibits the hydrocarbon chemistry in the gas from proceeding significantly beyond methyl radical production prior to encountering the substrate. Improvements in growth rate were modest, increasing by only a factor of two. Optical emission actinometry measurements indicate that the flux of atomic hydrogen across the stagnation layer to the substrate is mass diffusion limited. Since diamond growth depends upon the flux of atomic H to the substrate, these results suggest that under the conditions examined here, a low atomic H flux to the substrate poses an upper limit on the attainable diamond growth rate.

Synthesis of Monobactams via the Diastereoselective Kinugasa Reaction

Synthesis ◽  
2018 ◽  
Vol 50 (10) ◽  
pp. 1991-2000 ◽  
Author(s):  
Kamil Kabala ◽  
Barbara Grzeszczyk ◽  
Bartłomiej Furman ◽  
Marek Chmielewski ◽  
Jolanta Solecka ◽  
...  
Keyword(s):  
Biological Activity ◽  
Nitrogen Atom ◽  
Carbon Atom ◽  
Bulky Substituent ◽  
Protecting Group ◽  
Acetylene Molecule ◽  
Cyclic Nitrones ◽  
Lactam Ring

The Kinugasa reaction between phthalimidoacetylene and cyclic nitrones derived from l-phenylglycine or l-serine and glyoxylic acid­, catalyzed by copper(I) chloride in the presence of triethylamine, is reported. The acetylene molecule approaches the nitrone exclusively anti to the bulky substituent next to the nitrogen atom to provide the cis-substituted β-lactam ring preferentially. The six-membered oxazinone ring can be easily opened, the phthaloyl residue can be transformed into a Boc protecting group, and substituents at the C-4 carbon atom and the nitrogen atom of the β-lactam ring can be easily removed or transformed into groups suitable for further synthesis of a variety of monobactam structures. Selected synthesized compounds were evaluated for their biological activity, showing interesting properties.

Nucleation, Growth, and Microstructure of Nanocrystalline Diamond Films

MRS Bulletin ◽  
1998 ◽  
Vol 23 (9) ◽  
pp. 32-35 ◽  
Author(s):  
Dieter M. Gruen
Keyword(s):  
Atomic Hydrogen ◽  
Film Growth ◽  
Hydrogen Abstraction ◽  
Diamond Films ◽  
Chemical Vapor ◽  
Decisive Role ◽  
Theoretical Work ◽  
Diamond Lattice ◽  
Diamond Surface ◽  
Methyl Radical

It has been generally believed that hydrogen plays a central role in the various processes that have been developed over the years for the chemical vapor deposition (CVD) of diamond films. In particular it has been thought that atomic hydrogen is an absolutely essential ingredient of the vapor from which the films are grown. Typically in diamond CVD, gas mixtures consisting of l-vol% CH3 in 99-vol% H2 have been used in which atomic hydrogen is generated either by thermal decomposition or by collisional processes in a plasma. With a hydrocarbon precursor such as CH3, gas-phase hydrogen-abstraction reactions lead to the generation of the methyl radical CH3, which adsorbs on a carbon radical site also created by hydrogen abstraction from the hydrogen-terminated growing diamond surface. Additional hydrogen-abstraction reactions allow the carbon in the adsorbed methyl radical to form carbon-carbon bonds and thus be incorporated into the diamond lattice. Because graphite is thermodynamically more stable than diamond, the growth of metastable diamond has been thought to require the presence of atomic hydrogen, which has been said to stabilize the diamond lattice and to remove graphitic nuclei when they do form because of the preferential etching or regasification of graphite over diamond. This description of diamond-film growth from hydrocarbon–hydrogen mixtures is of course a very highly condensed version of the detailed experimental and theoretical work that has been carried out in the field over the years. However the predominant conclusion of most of that work is that, particularly in the absence of oxygen and perhaps halogens, atomic hydrogen plays a crucial and decisive role in diamond CVD.

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