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.

Optical Photoluminescence due to the Recombination of Donor-Acceptor Pairs in Porous Silicon

2000 ◽  
Vol 638 ◽  
Author(s):  
J. P. Zheng ◽  
X. Wei
Keyword(s):  
Porous Silicon ◽  
Temperature Dependence ◽  
High Temperatures ◽  
Thermal Energy ◽  
Low Temperatures ◽  
Ionization Energy ◽  
Photon Emission ◽  
Peak Wavelength ◽  
Exciton Recombination ◽  
Donor Acceptor

AbstractThe temperature dependence of the intensity, peak-wavelength, and bandwidth of photoluminescence (PL) spectra was studied in the porous silicon (PS) sample. To explain the observed temperature dependence, we proposed a model for the origin of the PL in PS. At low temperatures, the photon emission was dominated by the recombination of donor-acceptor pairs with ionization energies of about 4 meV. The donor and the acceptor were spatially separated with a distance of about 3.8 nm, which was about the crystalline size of the PS. Whereas at high temperatures where thermal energy exceeded the ionization energy, the photon emission was mainly from the exciton recombination.

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.

The role of H2O in enhancing hot filament assisted diamond growth at low temperatures

1997 ◽  
Vol 81 (3) ◽  
pp. 1536-1545 ◽  
Author(s):  
Z. Li Tolt ◽  
L. Heatherly ◽  
R. E. Clausing ◽  
C. S. Feigerle
Keyword(s):  
Low Temperatures ◽  
Diamond Growth ◽  
Hot Filament

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.

Magnetocrystalline Anisotropy of 3d6 and 3d4 Ions at Triclinic. Symmetry Sites Application to Fe2+ Ions in YIG: Me4+ (Me = Si, Ge)

1983 ◽  
Vol 38 (5) ◽  
pp. 540-554
Author(s):  
Czesław Rudowicz
Keyword(s):  
Free Energy ◽  
Temperature Dependence ◽  
Least Squares ◽  
High Temperatures ◽  
Low Temperatures ◽  
Present Model ◽  
Least Squares Method ◽  
Higher Order ◽  
Spin Hamiltonian ◽  
Doublet Model

The earlier suggested energy-level model based on an orbital singlet ground state for 3d6 and 3d4 ions at trigonal sites with large triclinic distortion is adopted to develop the single-ion theory of magnetic anisotropy. The Hamiltonian consisting of eight spin Hamiltonian terms and the molecular field is solved by perturbation theory. The resulting energies EMs with MS = 0, ± 1, ± 2 are applied to calculate the free energy for Fe2+ ions in Si- or Ge-substituted yttrium iron garnets where a uniform distribution of Fe2+ ions over the 12 inequivalent sites is assumed. It turns out that the first two cubic anisotropy constants K1, and K2 are insufficient to describe the anisotropy at high temperatures in the present model. By a least-squares method it is established that the anisotropy expansion series can be terminated at the fourth-order term for the present model. Thus K1, K2, K3 and K4 are derived analytically in terms of the free energy for some choosen directions of magnetization. The analytical results agree very well with the correspond­ing ones obtained by the least-squares method. The temperature dependence of Ki, i = 1. 2, 3, and 4, is calculated for a wide range of the spin Hamiltonian parameters (Bq(k)) and the molecular field (h). The theoretical K1, and K2 are fitted to the experimental values of K1, and K2 at low temperatures obtained by neglecting the higher-order anisotropy terms, to get the values of Bq(h) and for YIG:Si and YIG:Ge. A comparison of the present results with The corresponding ones of the previous doublet model, is also discussed. The theoretical account of the experimentally observed temperature dependence of the ratio K2/K1 for Fe2+ in YIG:Ge speak in favour of the present model rather than the doublet model. The change in sign of K1 observed for Fe2+ in YIG:Si, which could not be explained by the doublet model with uniform distribu­tion of Fe2+ ions, is well accounted for by the present model. The recently observed spin reorientation in YIG:Si can also be explained by the present model without resorting to a nonuniform distribution of Fe2+ ions required by the previous model. This study indicates that the higher-order constants K3 and K4 are significant at high temperatures according to the present model, whereas at low temperatures according to the doublet model. Hence an experimental determination of K3 and K4 over a wide temperature range may provide a test of the applicability of the two models.

Low Temperature Diamond Growth With CF4 Addition in A Hot Filament Reactor

1994 ◽  
Vol 349 ◽  
Author(s):  
Evaldo. J. Corat ◽  
V. J. Trava-Airoldi ◽  
Nélia F. Leite ◽  
Angel F.V. Peña ◽  
Vítor Baranauskas
Keyword(s):  
Growth Rate ◽  
Raman Spectroscopy ◽  
Low Temperature ◽  
Substrate Temperature ◽  
Low Temperatures ◽  
Diamond Growth ◽  
Gas Mixture ◽  
Hot Filament ◽  
Micro Balance

ABSTRACTIn this work we show that the addition of a small amount of CF4 to a regular CH4 -H2 gas mixture allows diamond growth at lower temperatures with reasonable growth rates. We used a hot filament assisted reactor and observed diamond growth with a substrate temperature as low as 390 ଌ. We present a comparative study for the growth dependence on substrate temperature with and without CF4 addition in the gas mixture. The growth rate is measured by post growth weighting with a micro balance. Raman spectroscopy, SEM and AFM images show the good quality of the films grown at low temperatures when CF4 is added to the feeding gas.

TEMPERATURE DEPENDENCE BEHAVIOR OF ELECTRICAL RESISTIVITY IN NOBLE METALS AT LOW TEMPERATURES

2014 ◽  
Vol 5 (3) ◽  
pp. 982-992 ◽  
Author(s):  
M AL-Jalali
Keyword(s):  
Experimental Data ◽  
Electrical Resistivity ◽  
Temperature Dependence ◽  
Concentration Dependence ◽  
Low Temperatures ◽  
Noble Metals ◽  
Phonon Scattering ◽  
Theoretical Models ◽  
Residual Resistivity ◽  
Electron Phonon Scattering

Resistivity temperature – dependence and residual resistivity concentration-dependence in pure noble metals(Cu, Ag, Au) have been studied at low temperatures. Dominations of electron – dislocation and impurity, electron-electron, and electron-phonon scattering were analyzed, contribution of these mechanisms to resistivity were discussed, taking into consideration existing theoretical models and available experimental data, where some new results and ideas were investigated.

Low solubility of alumina in enstatite and uncertainties in estimated palaeogeotherms

1978 ◽  
Vol 288 (1355) ◽  
pp. 471-486 ◽  
Keyword(s):  
High Temperatures ◽  
Low Temperatures ◽  
Alumina Content ◽  
Equilibrium Solubility ◽  
Low Solubility

Spurious kinks in estimated palaeogeotherms may result from small errors in the calibration of the geothermometers and geobarometers. New data indicate that the equilibrium solubility of alumina in enstatite is even less than shown by recent studies, and that the slopes (d T /d P ) of the isopleths of equal alumina content are steeper than hitherto believed. Consequently, pressures of equilibration estimated from current formulations of the orthopyroxene-garnet geobarometer will be too high at high temperatures (> 1200 °C) and too low at low temperatures.

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