Dynamisches Verhalten von Nanoclustern auf der Kupfer(111)-Oberflaeche

The shape and the motion of ion bombardment induced monatomic deep vacancy islands on Cu(111) are studied by means of a variable temperature scanning tunnelling microscope (STM). The aim is to identify the atomic mechanism of vacancy island motion. After a short introduction to the problems in understanding physical phenomena taking place on nanometer scale, a detailed description of the variable temperature STM is given, which was constructed especially for this purpose. The shape of the vacancy islands with diameters of 2-30 nm is studied between 250-350 K. The island size is stable for T #<=# 340 K on the experimental time scale. The equilibrium shape is found to be a hexagon with corners rounding off with increasing temperature. Furthermore, shape fluctuations around the equilibrium shape can be observed with the amplitudes of the relative fluctuation scaling non-linearly with the reciprocal island diameter. The dynamics of the coalescence of vacancy islands are discussed and the underlying mass transport mechanism can be derived from a continuum theory based scaling model: atoms should evaporate from the island boundary and diffuse across the vacancy island (terrace diffusion). It will be shown later on that the application of the scaling model is rather problematic. (orig.)93 refs.Available from TIB Hannover: RA 831(3475) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman