The effect of germanium on the desorption of hydrogen from Si(100)

• Published in: Surface science Vol. 295; no. 1; pp. 79 - 98
• Main Authors: Ning, Bob M.H., Crowell, John E.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 20.09.1993; Amsterdam Elsevier Science; New York, NY
• Subjects: Chemistry; Exact sciences and technology; General and physical chemistry; Solid-gas interface; Surface physical chemistry; Inorganic adsorbate; Hydrogen; Germanium; Desorption; Isotopic species; Silicon; Desorption spectroscopy; Inorganic adsorbent; Coverage rate; Surface
• DOI: 10.1016/0039-6028(93)90186-N
• ISSN: 0039-6028

The desorption of deuterium from Ge covered Si(100) surfaces has been studied using temperature programmed desorption. The presence of germanium on the surface generates a new low temperature state through which deuterium may desorb. The desorption maxima for all surface deuteride species are observed to shift to lower temperatures with increasing germanium coverage until the low temperature state becomes dominant at high surface hydride coverages and moderate to high germanium coverages. The general prominence of the low temperature feature is explained in terms of combined contributions from germanium monodeuteride and silicon dideuteride desorption. A single high temperature desorption feature is observed at low D atom exposures for θ Ge ⩽ 0.20 within this range, the β 1 desorption state shifts uniformly to lower temperatures with increasing Ge coverage. The shift in the β 1 desorption maxima from 805 K for Si(100) to 740 K for a 10.0% Ge Si(100) surface translates into a lowering of the desorption energy from 57.9 to 53.7 kcal mol . The lowered desorption energies for both silicon mono- and dihydrides are explained in terms of a lowered activation barrier for recombinative desorption; the presence of germanium lowers this barrier through electronic interactions with Si atoms.