Chlorine-induced Si surface segregation on the Ge-terminated Si/Ge(100) surface from core-level photoemission

Abstract

This study investigated the thermal reactions on the Cl-terminated Si/Ge(100)-2x1 surface using synchrotron radiation photoemission spectroscopy. Populations of surface Cl-Ge and CI-Si bonds during annealing are monitored by measuring the intensities of their corresponding Ge 3d, Si 2p, and Cl 2p core-level components. Experimental results clearly demonstrate that no Si atoms are present on the surface after the deposition of 0.8 monolayer Si on the Ge(100) surface at 730 K and that CI termination pulls out the indiffused Si of about two atomic layers deep to form Cl-Si bonds upon annealing at 550-690 K. We attribute such chlorine induced Si segregation to a thermodynamic driving force that favors the CI-Si surface species. Above 680 K, chlorine is desorbed in the form of SiCl2, although the top surface layer of the starting Si/Ge(100) sample consists of Ge-Ge dimers only.