Dynamic Force Microscopy Study on Si(111)root 3x root 3-Ag Using a Tuning Fork Atomic Force Microscope

By evaporating silver onto Si(111)7X 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)7X 7 reconstructed surface, the silver film assumes reconstructions such as root 3X root 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 root 3X root 3 reconstructed surface showed a double-well structure. We found evidence that the dissipation processes on the Ag islands and the root 3X root 3 reconstructed surface are induced by reversible tip modifications