Diamond Growth Rates and Quality: Dependence on Gas Phase Composition

1994 ◽  
Vol 339 ◽  
Author(s):  
William D. Cassidy ◽  
Edward A. Evans ◽  
Yaxin Wang ◽  
John C. Angus ◽  
Peter K. Bachmann ◽  
...  
Keyword(s):  
Growth Rates ◽  
Diamond Surface ◽  
Diamond Growth ◽  
Gas Composition ◽  
Chemical Potentials ◽  
Co Concentration ◽  
The Stability ◽  
Hot Filament ◽  
Tie Line

ABSTRACTDiamond growth rates and quality were studied as a function of source gas composition and correlated with position on the ternary C-H-O diagram. The chemical potentials of carbon and oxygen change dramatically on either side of the H2-CO tie line, leading to large differences in the equilibrium distribution of species. These differences are reflected in the species flux reaching the diamond surface, and hence in the quality and growth rate of the diamond. In situ microbalance measurements in a hot-filament reactor show that the reaction rate is independent of the CO concentration, but decreases with increasing O2. Quality, as measured by Raman spectroscopy, increases as the C/C+O ratio in the source gases is reduced to approach the critical value of 0.5. The stability of the filaments to decarburizing and oxidation are correlated with the carbon and oxygen chemical potentials and hence to the position on the C-H-O diagram. A preliminary ternary diagram for the C-H-F system is presented.

Chemical vapour deposition of diamond

1993 ◽  
Vol 342 (1664) ◽  
pp. 195-208 ◽  
Keyword(s):  
Chemical Vapour Deposition ◽  
Growth Rates ◽  
Atomic Hydrogen ◽  
Vapour Deposition ◽  
Chemical Vapour ◽  
Diamond Growth ◽  
Process Conditions ◽  
Diamond Crystals ◽  
Hot Filament

Growth of diamond at conditions where it is the metastable phase can be achieved by various chemical vapour deposition methods. Atomic hydrogen plays a major role in mediating rates and in maintaining a proper surface for growth. Low molecular weight hydrocarbon species (e.g. CH 3 and C 2 H x are believed to be responsible for extension of the diamond lattice, but complete understanding of attachment mechanisms has not yet been achieved. The nucleation of diamond crystals directly from the gas phase can proceed through a graphitic intermediate. Once formed, the growth rate of diamond crystals is enhanced by the influence of stacking errors. Many of the commonly observed morphologies, e.g. hexagonal platelets and (apparent) decahedral and icosahedral crystals, can be explained by the influence of simple stacking errors on growth rates. In situ measurements of growth rates as a function of hydrocarbon concentration show that the mechanism for diamond growth is complex and may involve surface adsorption processes in rate limiting steps. The transport régime in diamond deposition reactors varies widely. In the hot-filament and microwave reactors, which operate from 20 to 100 Torr (1 Torr ≈ 133 Pa), the transport of mass and energy is dominated by molecular diffusion. In the atmospheric pressure combustion and plasma methods, transport is dominated by convection. In situ measurements of H atom recombination rates in hot-filament reactors show that, under many commonly used process conditions, transport of atomic hydrogen to the growing surface is diffusion limited and H atom recombination is a major contributor to energy transport.

Quantitative In Situ Growth Measurements of Chlorine-Activated Homoepitaxial Diamond Cvd

1994 ◽  
Vol 349 ◽  
Author(s):  
Chenyu Pan ◽  
John L. Margrave ◽  
Robert H. Hauge
Keyword(s):  
Growth Rate ◽  
Substrate Temperature ◽  
Growth Rates ◽  
Diamond Growth ◽  
Flow Rates ◽  
Temperature Range ◽  
Quantitative Studies ◽  
Growth Activation ◽  
Lower Temperature

ABSTRACTIn situ quantitative studies of the effects of substrate temperature, methane and chlorine flow rates on homoepitaxial diamond growth rates on (110) surfaces in a chlorine-activated diamond CVD reactor have been carried out using a Fizeau interferometer. The temperature dependence of diamond growth rates was found to display three distinct growth activation energies, ranging from 9±2 kcal/mol in the substrate temperature of 750-950°C, to 3.2±0.2 kcal/mol in the temperature range of 300-650°C, followed by 1.2±0.2 kcal/mol in the temperature range of 102-250°C. Atomic hydrogen is believed to be the dominant activating species in the highest temperature range, and atomic chlorine is believed to be the dominant species in the lower temperature regions. Studies of the methane flow effect on diamond growth rates revealed a linearity, indicating that the diamond growth rate was of the first order in methane flows. Diamond growth rates were also found to increase linearly with the chlorine flow. At high chlorine flow rates, however, an accelerated diamond growth rate was observed. Discussion is given to explain the observed results.

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.

The Role of Heavy Hydrocarbons in Cvd Diamond Growth

1992 ◽  
Vol 270 ◽  
Author(s):  
Ching-Hsong Wu ◽  
T. J. Potter ◽  
M. A. Tamor
Keyword(s):  
Growth Rate ◽  
Cvd Diamond ◽  
Diamond Growth ◽  
Spectrometric Analysis ◽  
Heavy Hydrocarbons ◽  
Hot Filament Cvd ◽  
Hot Filament ◽  
Deposition Conditions

ABSTRACTA mass spectrometric analysis of heavy hydrocarbons (HHCs) during hot-filament CVD diamond growth was performed together with in situ monitoring of the growth rate. Many HHCs were detected and tentatively identified. Of all HHCs studied, only diacetylene shows good correlation with the diamond growth rate under various deposition conditions. Its possible role is discussed.

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.

Diamond Homoepitaxy Kinetics: Growth, Etching, and the Role of Oxygen

1994 ◽  
Vol 339 ◽  
Author(s):  
Robin E. Rawles ◽  
Mark P. D'Evelyn
Keyword(s):  
Temperature Dependence ◽  
High Temperatures ◽  
Low Temperatures ◽  
Diamond Surface ◽  
Diamond Growth ◽  
Minimal Amount ◽  
Rate Behavior ◽  
Etch Rates ◽  
Apparent Activation Energies ◽  
Hot Filament

ABSTRACTGrowth and etch rates for diamond homoepitaxy have been measured in situ using Fizeau interferometry. Experiments were conducted in a hot-filament reactor using hydrogen, methane, and oxygen feed gases at a reactor pressure of 25 torr. The substrate temperature dependence for growth on diamond(lOO) was studied for 0.5% and 1% CH4 and 0–0.44% O2. Apparent activation energies of 17 and 5 kcal/mol were determined for growth from 0.5% and 1% CH4 in hydrogen, over the ranges of 700 – 1000 °C and 800 – 1050 °C, respectively. When a minimal amount of Oxygen was added to the feedstock, the growth-rate behavior was similar for that with pure methane. With greater amounts of added oxygen, growth rates were higher than those without Oxygen at low temperatures, proceeded through a maximum, and then decreased until etching was observed at high temperatures. Similar behavior was observed for growth from 1% CH4 with and without oxygen. We also measured the temperature dependence for etching of homoepitaxial diamond films in hydrogen with 0–0.1% O2, and observed etch rates of 0.01 – 0.1 microns/hr in the range of 950 – 1150 °C. We propose that oxygen facilitates diamond growth at low temperatures by enhancing the removal of both sp2- and sp3-bonded “errors” and/or by increasing the efficiency of carbon incorporation by roughening the diamond surface, and that these etching processes become dominant at high temperatures.

Uncoupling crystal growth and nucleation in the deposition of diamond from the gas phase

1992 ◽  
Vol 7 (7) ◽  
pp. 1778-1787 ◽  
Author(s):  
E. Molinari ◽  
R. Polini ◽  
M.L. Terranova ◽  
P. Ascarelli ◽  
S. Fontana
Keyword(s):  
Gas Phase ◽  
Growth Rates ◽  
Diamond Surface ◽  
High Catalytic Activity ◽  
Fast Reaction ◽  
Sem Images ◽  
Atom Concentration ◽  
Hot Filament ◽  
Proper Consideration

Diamond deposits of well-separated particles have been obtained by the hot filament CVD technique on Si(100) wafers. Particle counting in SEM images and determination of their linear dimensions require a separate study of growth rates and of nucleation densities as a function of time, substrate temperature (500 °C–950 °C), gas phase composition (0.5–2% CH4 in H2), and total pressure (15–76 Torr). It is shown that recent models proposed for the growth process can successfully be applied if proper consideration is given to the high catalytic activity of the growing diamond surface for the heterogeneous recombination of gaseous H-atoms. This fast reaction controls the H-atom concentration at the surface and couples growth rates and nucleation densities via the gas phase.

Surface Stability and Electronic Structure of Hydrogen and Fluorine Terminated Diamond Surfaces: a First Principles Investigation

2008 ◽  
Vol 1130 ◽  
Author(s):  
Fatih Gurcag Sen ◽  
Yue Qi ◽  
Ahmet T Alpas
Keyword(s):  
Electronic Structure ◽  
First Principles ◽  
Surface Composition ◽  
Close Packing ◽  
Diamond Surface ◽  
Surface Stability ◽  
Diamond Surfaces ◽  
Large Size ◽  
Chemical Potentials ◽  
The Stability

AbstractThe stability and electronic structure of fully H or F terminated and mixed H and F terminated diamond (111) surfaces were studied using first principles calculations. It was found that F atoms on the surface, like H, formed sp3 type bonding with C atoms, which resulted in a more stable 1×1 configuration rather than the π-bonded 2×1 construction of clean diamond. A phase diagram showing the stable surface composition regions was constructed as a function of chemical potentials of H and F. The diagram shows that the surface with 75% F (25% H) termination was unstable. The F terminated surface was more stable than H termination due to the formation of strong ionic C-F bonding and the close packing of the large F atoms. Due to the attractive forces developed between F atoms, a close packed surface was formed. Additionally, the exposure of C to the environment became restricted because of the large size of F atoms. Hence, F terminated diamond surface was more chemically inert compared to H terminated surface. To bring two F terminated surfaces together, a large repulsive force was required due to the negative charge on F atoms, and this led to low adhesion between two F terminated diamond surfaces compared to two H terminated surfaces.

Diamond growth using carbon monoxide as a carbon source

1992 ◽  
Vol 7 (5) ◽  
pp. 1195-1203 ◽  
Author(s):  
F.M. Cerio ◽  
W.A. Weimer ◽  
C.E. Johnson
Keyword(s):  
Carbon Source ◽  
Gas Phase ◽  
Growth Rates ◽  
Microwave Plasma ◽  
Polycrystalline Diamond ◽  
Chemical Mechanism ◽  
Diamond Surface ◽  
Diamond Growth ◽  
Lower Growth ◽  
Temperature Combustion

Polycrystalline diamond films were produced in a microwave plasma assisted CVD reactor using CO as the carbon source gas. Reactor exhaust gas compositions were determined by mass spectrometry using 2–10% CO and 0–1.5% O2 in H2 feed gas mixtures. The chemistry involved in the gas phase is similar to that which occurs when diamond is grown using hydrocarbons as carbon source gases. A chemical mechanism for the oxidation of CH4 in flames appears to be applicable to this system. Addition of O2 to the reactor feed gas results in increased growth rates for low addition levels possibly due to activation of the diamond surface, while lower growth rates result at high addition levels due to oxidation of carbon from the surface and depletion of diamond growth precursors in the gas phase. The chemical reactions that take place in the plasma are similar to those that occur in flames and hot filament reactors, indicating that the plasma acts to induce reactions that are normally associated with high temperature combustion processes.

Sign in / Sign up

Export Citation Format

Share Document