ADSORPTION OF ATOMIC-HYDROGEN ON SI(100)-2X1 AT 400-K

At 400 K, the absolute coverage of hydrogen (deuterium) adsorbed on the Si(100)-2 X 1 surface for different hydrogen-induced surface reconstruction phases was determined by nuclear reaction analysis and low-energy electron diffraction. The transition from a monohydride 2 X 1 phase to a dihydride plus monohydride 3 X 1 phase results in a distinct plateau on the curve of coverage versus exposure. With increasing atomic hydrogen (deuterium) exposure the coverage increases to about 1.7 monolayers with concomitant deterioration of the 3 X 1 phase, indicating etching of silicon backbonds. Prolonged exposure leads to an effective saturation coverage of 1.6 +/- 0.1 monolayers with further degradation of the 3 X 1 symmetry.