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 $\mathrm{S}\mathrm{i}/\mathrm{G}\mathrm{e}(100)\ensuremath{-}2\ifmmode\times\else\texttimes\fi{}1$ surface using synchrotron radiation photoemission spectroscopy. Populations of surface Cl--Ge and Cl--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 Cl 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 Cl--Si surface species. Above 680 K, chlorine is desorbed in the form of ${\mathrm{SiCl}}_{2},$ although the top surface layer of the starting Si/Ge(100) sample consists of Ge--Ge dimers only.