Evolution of surface structures on Si(001) during hydrogen desorption

We have examined atomistic processes of hydrogen desorption from the H/Si(001) surface by scanning tunneling microscopy (STM). At a low hydrogen dose, Si atoms are etched from the surface and the patched pattern of 2 x 1 and 1 x 2, where each step edge penetrates into neighboring steps, is observed. On the other hand, a quasi-stable c(4 x 4) surface reconstruction is observed for high doses of hydrogen before the complete recovery of the 2 x 1 structure. It is found that the formation of the c(4 x 4) structure needs a rather large density of vacancies and that the domains are pinned at the clusters and disordered areas on the surface. (C) 1997 Elsevier Science B.V.