In situ infrared monitoring of electrochemical adsorption/desorption of hydrogen on germanium

In an acidic electrolyte, germanium exhibits voltammetric peaks which have been ascribed to a change between a hydrogenated and a hydroxylated surface. Using in situ infrared spectroscopy, we have obtained clearcut confirmation of this prediction. GeH and GeH2 species are identified at the hydrogenated surface. The bidentate Ge sites are hydrogenated and reoxidized at more positive potentials than the monodentates. The roughness of the surfaces on the atomic scale accounts for the dependence of the absorption intensities upon infrared polarization and crystal orientation. The various voltammetric peaks are correlated with the reversible adsorption/desorption of hydrogen on steps and (111) facets.