Structure of a passivated Ge surface prepared from aqueous solution

The structure of a passivating sulfide layer on Ge(001) was studied using X -ray standing waves and X-ray fluorescence. The sulfide layer was formed by reacting clean Ge substrates in (NH4)(2)S solutions of various concentrati ons at 80 degrees C. For each treatment, a sulfide layer containing approxi mately two to three monolayers (ML) of S was formed on the surface, and an ordered structure was found at the interface that contained approximately 0 .4 ML of S. Our results suggest the rapid formation of a glassy GeSx layer containing 1.5-2.5 ML S residing atop a partially ordered interfacial layer of bridge-bonded S. The passivating reaction appears to be self-limited to 2-3 ML at this reaction temperature. (C) 2000 Elsevier Science B.V. All ri ghts reserved.