Münster 1997 – wissenschaftliches Programm

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O: Oberflächenphysik

O 26: Methodisches (Experiment)

O 26.12: Vortrag

Mittwoch, 19. März 1997, 18:45–19:00, BOT

NON CONTACT AFM STUDIES IN UHV OF SEMICONDUCTORS AND INSULATORS — •CH. LOPPACHER, M. BAMMERLIN, M. GUGGISBERG, J. LÜ, R. LÜTHI, E. MEYER, and H.-J. GÜNTHERODT — Institut für Physik Universität Basel Klingelbergstrasse 82
CH-4056 Basel Schweiz.

With the method of Non-Contact Atomic Force Microscopy (NC-AFM) under the conditions of ultrahigh vacuum (UHV), we perform studies of pure semiconductors and insulators. Results with true atomic resolution on these materials are presented. As a second point three different ways of detecting the frequency shift in NC-AFM are discussed: 1) The slope detection, where damping and frequency shift cannot be distinguished. 2) FM-Detection, where frequency shifts are measured, but damping is a function of the phase between the cantilever oscillation and the excitation signal. FM-Detection does not control the phase to a constant value. 3) We developped a new method of frequency detection based on the technique of Phase Locked Loop (PLL). With PLL techniques we can measure frequency shifts and damping as we keep the phase constant. The advantage of this technique is discussed.