In:
The Journal of Chemical Physics, AIP Publishing, Vol. 131, No. 4 ( 2009-07-28)
Abstract:
This article reports systematic measurements of the power utilization by Ta (and Re) hot filaments (HFs) operating in a poor vacuum, in pure He, N2, and H2, and in CH4/H2 gas mixtures of relevance to diamond growth by HF chemical vapor deposition, as functions of filament temperature Tfil (in the range of 1800–2700 K) and gas pressure p (in the range of 10−2–100 Torr). In the cases of H2 and the CH4/H2 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∼10–20 Torr and thereafter to remain constant or, at the highest Tfil, 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 H2 to a two-step mechanism involving H atom formation by dissociative adsorption at bare (S∗) sites and by desorption at hydrogenated (SH) sites on the HF surface.
Type of Medium:
Online Resource
ISSN:
0021-9606
,
1089-7690
Language:
English
Publisher:
AIP Publishing
Publication Date:
2009
detail.hit.zdb_id:
3113-6
detail.hit.zdb_id:
1473050-9
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