Berlin 2015 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 79: Scanning Probe Techniques: STM

O 79.4: Vortrag

Donnerstag, 19. März 2015, 11:15–11:30, HE 101

A Self-Tracking Spectroscopic Method for Surface Photovoltage Measurements on Semiconducting Surfaces — •Kevin Oldenburg, Stefan Polei, Sylvia Speller, and Ingo Barke — University of Rostock, Institute of Physics, 18051 Rostock, Germany

Spatially resolved surface photovoltage (SPV) measurements by means of scanning tunneling microscopy enable access to the local band topology at semiconductor surfaces. In the presence of metallic surface states the SPV can be easily obtained from I(V) curves under continuous wave (cw) illumination [1]. For semiconducting surfaces, however, the weak Fermi level pinning leads to tip induced band bending [2] that is difficult distinguish from the effect of the SPV under cw conditions. We present a new experimental approach that automatically keeps the electric field between tip and sample constant with respect to the light intensity by tracking the SPV simultaneously with its measurement. The method is benchmarked for the case of Si(100)-c(4x2) at different bulk doping levels. The role of tip-induced band bending is discussed in comparison to alternative techniques.

[1] K. Sell et al., Phys. Stat. Sol. B 247, 1087 (2010).

[2] M. McEllistrem, G. Haase, D. Chen, and R. J. Hamers, Phys. Rev. Lett. 70, 2471 (1993).