Regensburg 2010 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 11: Methods: Scanning probe techniques II

O 11.2: Vortrag

Montag, 22. März 2010, 15:15–15:30, H32

Investigating the voltage dependence of the apparent barrier height in scanning tunneling microscopy — •Michael Becker and Richard Berndt — Institut für Experimentelle und Angewandte Physik, Christian-Albrechts-Universität zu Kiel, D-24098 Kiel, Germany

Scanning tunneling microscopy measurements of the apparent height of the tunneling barrier on noble metal (111) surfaces and for Pb islands on Ag(111) are analyzed. The apparent barrier height (ABH) is found to vary significantly with the bias voltage. In particular for the coinage metal surfaces, the ABH is asymmetric with respect to the bias polarity, in contrast to simple interpretations in terms of an average work function of tip and sample. For Pb/Ag(111) the bias dependence leads to drastic changes and even inversion of contrast in spatial maps of the ABH. Model calculations of the tunneling current, which take band structure effects into account, describe the experimental observations. Financial support by the Deutsche Forschungsgemeinschaft through SFB 668 is acknowledged.