COMPARISON OF THE FIRST STAGES OF THE ADSORPTION OF PB AND GE ON THE SI(111)7X7 SURFACE

Experimental results show that, at low coverage, Pb atoms adsorbed on Si(111)7 x 7 preferentially agglomerate, forming dimers, trimers or te tramers. Following our recent calculations, there is no tendency to ag glomeration in the case of Ge adsorption on this surface. We present a comparative study of various adsorption mechanisms for Ge and Pb on S i(111)7 x 7 in the framework of the crystalline extension of the exten ded Huckel theory. We consider the possibility of adsorption of Pb and Ge on dangling bond (DB) sites as well as different positions between the Si DB sites. By means of adsorption energy and overlap population studies, we discuss the differences of the behaviour between Ge and p h interacting with Si(111)7 x 7. (C) 1998 Elsevier Science B.V. All ri ghts reserved.