Investigations of the Surface Chemical Composition and Atomic Structure of ex-situ Sulfur Passivated Ge(100)

Abstract

Using complementary surface analysis techniques, we have studied the chemical and structural properties of the S/Ge(100) passivation layer formed upon sulfidation in an aqueous (NH4)2S solution. Our experiments have revealed that only S-Ge bonds are formed upon the adsorption of S and that the surface is essentially free of other S-containing species (i.e. Sn or SOx). The passivation treatment was found to reduce, but not to fully inhibit Ge-O bonds on the surface. Moreover, we have shown that the top-layer of the passivated surface shows a high degree of disorder even though it is associated with a spotty (1x1) RHEED pattern. Based on our experimental findings, we conclude that the passivation layer can be best described as a thin amorphous GeSxOy film atop a partially ordered interfacial layer, a surface model that has been proposed previously in literature.