Scanning tunneling spectroscopy is used to study -type surfaces over the temperature range . Surface states arising from adatoms and rest atoms are observed. With consideration of tip-induced band bending, a surface band gap of separating the bulk valence band from the surface adatom band is deduced. Peak positions of adatom states are located at energies of and 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 . The rest-atom spectral peak, observed at 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.71.1253167 More
- Received 30 September 2004
- Published 15 March 2005
© 2005 The American Physical Society