Dynamic Force Microscopy Study on Si(111).RAD.3*.RAD.3-Ag Using a Tuning Fork Atomic Force Microscope

Abstract

By evaporating silver onto Si(111)7× 7 surfaces, heterogeneous samples can be prepared that enable the direct comparison of surfaces with very different characteristics. In contrast to the bare Si(111)7× 7 reconstructed surface, the silver film assumes reconstructions such as √3×√3, and (111) oriented silver islands may also be present depending on the degree of coverage and the annealing or growth temperature. In the present study, force-distance spectra are measured using a home-built low-temperature tuning fork atomic force microscope. The focus of this work is a comparative study of different types of surfaces using the same tip in order to form an understanding of dissipation in non-contact atomic force microscopy. Force spectroscopic studies of the Ag islands revealed two different types of spectra occurring with the same probability. In some cases, the frequency shift-distance (df-z) spectra exhibited the commonly observed distance dependence in the attractive regime with a single minimum. In other cases, df-z spectra exhibited a double minimum, which corresponds to the dissipation process. In contrast to the measurements on the Ag islands, all df-z spectra from the √3×√3 reconstructed surface showed a double-well structure. We found evidence that the dissipation processes on the Ag islands and the √3×√3 reconstructed surface are induced by reversible tip modifications. [DOI: 10.1380/ejssnt.2011.26]