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O: Oberflächenphysik

O 15: Raster-Kraft-Mikroskopie II

O 15.3: Vortrag

Dienstag, 18. März 1997, 10:00–10:15, BOT

LOCAL CONTACT POTENTIAL MEASUREMENTS ACROSS STEPS OF THE Si(111)7×7 SURFACE IN ULTRAHIGH VACUUM — •M. GUGGISBERG, M. BAMMERLIN, R. LÜTHI, F. BATTISTON, J. LÜ, C. LOPPACHER, E. MEYER, and H.-J. GÜNTHERODT — Institut für Physik, Universität Basel, Klingelbergstrasse 82,
CH-4056 Basel, Schweiz.

We used an atomic force microscope (AFM) to measure the contact potential locally (Kelvin Probe Microscopy). The instrument is implemented in an ultrahigh vacuum (UHV) system and is operated in the so-called dynamic non-contact mode. A novel spectroscopy technique allows to sweep the bias voltage U between tip and sample and to acquire the resulting frequency shift Δ f. By this technique Δ f vs. U curves are obtained from which the contact potentials can be determined quantitatively and locally between Si-tip and sample. As an example we demonstrate the successful application of this method to the Si(111)7×7 reconstructed surface. We find a discontinuity of the contact potential across steps of Si(111)7×7, which will be discussed in terms of a simple model.