On the mechanism of H atom production in hot filament activated H{sub 2} and CH{sub 4}/H{sub 2} gas mixtures
- School of Chemistry, University of Bristol, Bristol BS8 1TS (United Kingdom)
- Skobel'tsyn Institute of Nuclear Physics, Moscow State University, Leninskie Gory, Moscow 119991 (Russian Federation)
This article reports systematic measurements of the power utilization by Ta (and Re) hot filaments (HFs) operating in a poor vacuum, in pure He, N{sub 2}, and H{sub 2}, and in CH{sub 4}/H{sub 2} gas mixtures of relevance to diamond growth by HF chemical vapor deposition, as functions of filament temperature T{sub fil} (in the range of 1800-2700 K) and gas pressure p (in the range of 10{sup -2}-100 Torr). In the cases of H{sub 2} and the CH{sub 4}/H{sub 2} gas mixtures, the power consumption studies are complemented by in situ measurements of the relative H atom densities [H] near the HF--which are seen to maximize at p{approx}10-20 Torr and thereafter to remain constant or, at the highest T{sub fil}, to decline at higher p. These (and many previous) findings are rationalized by a companion theoretical analysis, which reduces the complex array of chemisorption and desorption processes that must contribute to the HF-surface mediated dissociation of H{sub 2} to a two-step mechanism involving H atom formation by dissociative adsorption at bare (S{sup *}) sites and by desorption at hydrogenated (SH) sites on the HF surface.
- OSTI ID:
- 21559752
- Journal Information:
- Journal of Chemical Physics, Journal Name: Journal of Chemical Physics Journal Issue: 4 Vol. 131; ISSN JCPSA6; ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
Similar Records
Catalytic reduction of CO with hydrogen sulfide. 3. Study of adsorption of O/sub 2/, CO, and CO coadsorbed with H/sub 2/S on anatase and rutile using Auger electron spectroscopy and temperature-programmed desorption
A study of the dissociation of CH{sub 3}CH{sub 2}SH{sup +} by collisional activation: Evidence of nonstatistical behavior
Related Subjects
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ADSORPTION
ALKANES
ATOMS
CARBON
CHEMICAL COATING
CHEMICAL REACTIONS
CHEMICAL VAPOR DEPOSITION
CHEMISORPTION
DEPOSITION
DESORPTION
DIAMONDS
DISPERSIONS
DISSOCIATION
ELEMENTS
FILAMENTS
FLUORINE COMPOUNDS
HALOGEN COMPOUNDS
HYDROCARBONS
HYDROFLUORIC ACID
HYDROGEN
HYDROGEN COMPOUNDS
INORGANIC ACIDS
INORGANIC COMPOUNDS
METHANE
MINERALS
MIXTURES
NONMETALS
ORGANIC COMPOUNDS
SEPARATION PROCESSES
SORPTION
SURFACE COATING
SURFACES