HYDROGEN-INDUCED REORDERING OF THE SI(111)(ROOT-3X-ROOT-3)-BI SURFACESTUDIED BY SCANNING-TUNNELING-MICROSCOPY

We report results of a scanning tunneling microscopy investigation of the process of hydrogen adsorption on bismuth-deposited Si(111) surfac es. Two domains with the root 3 X root 3 periodicity are contained in the Si(111)(root 3 X root 3)-Bi surface, i.e., a low Bi-coverage root 3 domain (named alpha-phase) and a high Bi-coverage root 3 domain (bet a-phase). When atomic hydrogen adsorbs on the Si(111)(root 3 x root 3) -Bi surface, we found that (1) hydrogen atoms adsorb on the alpha-phas e in preference to the beta-phase, (2) Bi atoms are displaced from the ir original positions, and (3) bulk-like 1 X 1 surface structures appe ar in the restlayer. (C) 1998 Elsevier Science B.V.