Ambient stability of chemically passivated germanium interfaces

The stability of any semiconductor surface passivating layer is key to applications. Second harmonic generation (SHG) can be used to probe the chemical state of semiconductor interfaces, as well as investigate the mechanisms of chemical transformation. While the SHG rotational anisotropy changes upon sulfidation or alkylation of Ge surfaces, SHG appears far less sensitive to H and Cl passivation of germanium surfaces than to silicon surfaces. Investigation of the stability of chemically modified germanium surfaces using a number of additional techniques, including atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS), reveals that H- and Cl-terminated Ge(1 1 1) rapidly re-oxidize in ambient. S- and alkyl-terminations are more robust, showing little sign of oxide formation after a month in ambient.