title: Mechanism of the potential-triggered surface transformation of germanium in acidic medium studied by ATR-IR spectroscopy.
abstract: In acidic solution, germanium surfaces undergo a transformation to hydrogen-terminated surfaces at sufficiently negative electrode potentials. Herein, we used in situ and operando attenuated total reflection infrared (ATR-IR) spectroscopy coupled to electrochemical experiments to study the details of this surface transformation on Ge(111) and Ge(100) in 0.1 M HClO4. The ATR-IR data gathered during the surface transformation are consistent with an interpretation according to which an intermediate state exists of a surface with mixed termination. In the mixed termination, both H and OH are bound to the surface, which showed a Ge-H stretching mode at ∼2025-2030 cm-1. At sufficiently negative potentials, the surfaces became fully hydrogen terminated. ATR-IR spectra can be understood by assigning the peak at ∼1977-1990 cm-1to the stretching mode of GeH1species on Ge(111), and the peak at ∼2000-2015 cm-1to a stretching mode of GeH2species on Ge(100). Measurements of the linear dichroism showed the GeH1species to be oriented predominantly upright. The transition dipole moment of the GeH2species was oriented parallel to the surface, as expected for an antisymmetric stretching mode.
authors.affiliation: Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Str. 1, 40237, Düsseldorf, Germany. a.erbe@mpie.de, aerbe@arcor.de.
authors.forename: Simantini
authors.identifier: http://orcid.org/0000-0002-0105-9771
authors.initials: S
authors.lastname: Nayak
authors.affiliation: Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Str. 1, 40237, Düsseldorf, Germany. a.erbe@mpie.de, aerbe@arcor.de and Department of Materials Science and Engineering, NTNU, Norwegian University of Science and Technology, 7491 Trondheim, Norway.
authors.forename: Andreas
authors.initials: A
authors.lastname: Erbe