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O: Oberflächenphysik

O 17: Elektronische Struktur (Experiment und Theorie) II

O 17.3: Vortrag

Dienstag, 9. März 2004, 11:45–12:00, H36

STM-Thermovoltage measurements of surface electronic states on Ag/Au(111) — •Winfried Langenkamp, Bastian Weyers, and Rolf Möller — Universität Duisburg-Essen, Institut für Experimentelle Physik, Universitätsstr. 3-5, 45141 Essen

Submonolayer films of silver on Gold(111) have been examined with a thermovoltage-STM to determine the shift in the fermi wavelength of surface state electrons.

If tip and sample of an STM are at different temperatures, a thermovoltage arises which is correlated to the derivative of the sample’s density of electronic states at the fermi level.

This voltage is measured by a feedback loop for a bias voltage tuning the average current to zero. Simultaneously the tip-sample separation is adjusted by the current resulting from a small alternating bias voltage.

The thermovoltage can be used to analyze atoms of different chemical nature and standing waves of surface state electrons. [1]

In the experiments discussed the equivalent of less then a monolayer of Ag was evaporated on Au(111) leading to the formation of silver islands of monoatomic height. The thermovoltage provides information to distinguish gold and silver areas below the tip as well as on the standing waves of surface states on Au(111) and on 1 ML Ag/Au(111).

[1] D. Hoffmann et al., Thermovoltage in scanning tunnelling microscopy, J. Electron Spectroscopy, 109 (2000) 117