RTM-Untersuchung dynamischer Prozesse auf Cu(111)-Oberflaechen am Beispiel von Stufenfluktuationen und epitaktisch gewachsenen Nanostrukturen

This thesis deals with the investigation of atomic mass transport on Cu(111)-surfaces using scanning tunneling microscopy (STM). The aim of this work was to characterize the relevant microscopic processes and their respective energies. Equilibrium step fluctuations have been studied between 305 K and 600 K. The results indicate that atomic diffusion along the step edge dominates the dynamics of steps. For this process an upper limit for the activation barrier has been obtained. For temperatures higher than 550 K, indications for a dominant diffusion across terraces exist. The decay of single layer high (or deep) adatom- and vacancy islands (Ostwald rippening) on Cu(111) has been investigated between 300 and 360 K. From the temperature dependence of the decay and from numerical calculations of the rate limiting processes and the relevant energies have been obtained. The investigation of the decay of multilayer islands yielded a very unexpected behaviour. At steps on the Cu(111)-surface a step edge barrier slows down the interlayer mass transport. This barrier vanishes completely if two steps meet to form a ledge contact. In this case a strongly enhanced interlayer diffusion sets in (landslide effect). To date no theoretical explanation for this behaviour is avalaible. (orig.)117 refs.Available from TIB Hannover: RA 831(3588) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman