TOF-ICISS OBSERVATION OF PB GROWTH ON THE SI(111)-ROOT-3X-ROOT-3-AG SURFACE

We have investigated the Pb thin film growth on Si(111)-7 X 7 and Si(1 11)-root 3 x root 3-Ag surfaces at room temperature using time-of-flig ht impact collision ion scattering spectroscopy (TOF-ICISS). From the angle-resolved TOF spectra of the Pb film grown onto each of these two different substrates, we found that AgO atoms on the Si(111) surface promote epitaxial growth of Pb film at room temperature. The crystalli ne quality of Pb(111) overlayers grown on the Si(111)-root 3 X root 3- Ag surface is much better than that grown on the clean Si(111)-7 X 7 s urface, although the growth of the Pb film on the former surface occur s by the Stranski-Krastonov (SK) growth mode as well as the growth on the latter. In the presence of the root 3 x root 3-Ag layer, the Pb ov erlayer epitaxially grows with the orientation of Pb(111)[01 (1) over bar]parallel to Si(111)[01 (1) over bar], which is the same as for the one grown on the clean Si(111)-7 x 7 surface. Also, we have found tha t the coverage of the 2D Pb layer in the SK growth is 1.35 ML on the S i(111)-7 x 7 surface, while it is 1.0 ML on the Si(111)-root 3 X root 3-Ag surface.