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TT: Tiefe Temperaturen

TT 17: Anwendungen der Supraleitung: Tieftemperatur-Teilchendetektoren und -Experimentiertechniken

TT 17.9: Hauptvortrag

Donnerstag, 27. März 2003, 11:45–12:15, HSZ301

Scanning Force Microscopy at Low Temperatures: Interatomic Forces — •H. J. Hug, M. A. Lantz, R. Hoffmann, M. Martin und H.-J. Guentherodt — Institute of Physics, Klingelbergstr. 82, CH-4056 Basel, Switzerland

Low temperature scanning force microscopy has permitted to obtain high quality images and to measure the frequency shift as a function of the tip-sample distance above specific lattice sites on the Si(111)-7x7, and the KBr(001) surface. In the case of Silicon, the short-range force extracted from the frequency-distance data agreed well with first principle calculations indiacting the formation of a single covalent bond. With chemically inactive tips much weaker force of electrostatic nature were found. In contrast to covalent surfaces on which atoms with dangling bonds are imaged, on alkali halide surfaces, one type of ions is imaged as bright, the other as dark, presumably depending on the charge of the imaging ion located at the tip apex. The identification of the sublattice is difficult, because the arrangement is highly symmetric and, in addition, the ionic radii are nearly similar. Nevertheless, the sublattice could be identified from a comparison of calculated force to data obtained at top, hollow, and bridge sites, respectively.