Low-temperature tunneling spectroscopy of Ge(111)c(2×8) surfaces

Phys. Rev. B 71, 125316 – Published 15 March 2005
R. M. Feenstra, S. Gaan, G. Meyer, and K. H. Rieder


Scanning tunneling spectroscopy is used to study p-type Ge(111)c(2×8) surfaces over the temperature range 7to61K. Surface states arising from adatoms and rest atoms are observed. With consideration of tip-induced band bending, a surface band gap of 0.5±0.1eV separating the bulk valence band from the surface adatom band is deduced. Peak positions of adatom states are located at energies of 0.09±0.02eV and 0.24±0.03eV above this gap. A spectral feature arising from the inversion of the adatom state occupation is also identified. A solution of Poisson’s equation for the tip-semiconductor system yields a value for the interband current in agreement with the observations, for an assumed tip radius of 100nm. The rest-atom spectral peak, observed at 1.0eV below the valence band maximum, is observed to shift as a function of tunnel current. It is argued that nonequilibrium occupation of disorder-induced surface states produces this shift.

DOI: http://dx.doi.org/10.1103/PhysRevB.71.125316

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  • Received 30 September 2004
  • Published 15 March 2005

© 2005 The American Physical Society

Authors & Affiliations

R. M. Feenstra* and S. Gaan

  • Department of Physics, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA

G. Meyer

  • Paul Drude Institut für Festkörperelektronik, Hausvogteiplatz 5–7, 10117 Berlin, Germany

K. H. Rieder

  • Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14, 14195 Berlin, Germany

  • *Email address: feenstra@cmu.edu
  • Present address: IBM Research Division, Zurich Research Laboratory, 8803 Rüschlikon, Switzerland.

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