First-principles studies of hydrogenated Si(111)-7x7

The relaxed, geometries and electronic properties of the hydrogenated phases of the Si(111)-7x7 surface are studied using first principles molecular dynamics. A monohydride phase, with one H per dangling bond adsorbed on the bare surface, is found to be energetically favorable. Another phase where 43 hydrogens saturate the dangling bonds created by the removal of the adatoms from the clean surface is found to be nearly equivalent energetically. Experimental scanning tunneling microscopy and differential-reflectance characteristics of the hydrogenated surfaces agree well with the calculated features.