ISSN:
1089-7690
Source:
AIP Digital Archive
Topics:
Physics
,
Chemistry and Pharmacology
Notes:
The low energy electron diffraction technique was used to study the hydrogen chemisorption induced structural instability on the diamond C(111) surface. From the quantitative analysis of diffraction spots intensity on the as-dosed, partially desorbed, and annealed hydrogenated C(111) surfaces, the correlation between the (1×1)↔(2×1) phase transformation, hydrogen coverage, and surface temperature is shown. Thermal treatment with partial hydrogen desorption on the fully hydrogenated C(111) surface induces a (1×1)–(2×1) reconstruction with the observable half-order spots intensity (I1/2) emerging only after heating the substrate to 1270 K. Conversely, thermal annealing of the partially hydrogenated C(111) surface without desorbing H causes the size shrinking of the (2×1) domains as well as the relaxation of the hydrogenated domains. The temperature effect of I1/2 summarized from both thermal studies reveals that the (2×1) domain instability originated from the relaxation of the hydrogenated domains at elevated temperatures. In addition, the H chemisorption behavior on C(111) at different surface temperatures suggests that the terrace edges could be the preferential sites for the initial H adsorption and the growth of the hydrogenated domains might predominantly start from the terrace boundaries at a surface temperature as low as 125 K. The present study also allows us to tentatively propose that there might exist a low-temperature chemisorption state in addition to the hydrogenated metastable state as suggested by the sum-frequency generation spectroscopy and theoretical studies. A possible mechanism for the hydrogen chemisorption induced structural transformation is also discussed. © 1998 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.477617
Permalink
