In situ infrared monitoring of hydrogen adsorption desorption at a germanium electrode

Upon potential cycling in acidic electrolyte, the coverage of Ge electrodes call be changed from GeH to GeOH. In situ infrared spectroscopy reveals th at hydrogen adsorbs and desorbs at Ge in mono- and dihydride configurations . Comparison of (111)- and (100)-oriented electrodes shows that the Ge surf ace is rough at the atomic scale and that this roughening takes place throu gh(lll) microfacetting. This facetting call account for the attenuated pola rization dependence of the GeH absorption and its enhancement through local field effects. Finally, the band edge shifts which are observed upon hydro gen adsorption/desorption appear related to a change in the Ge surface char ge rather than to a dipolar effect. (C) 1999 Elsevier Science B.V. All righ ts reserved.