RTM Untersuchungen an zweidimensionalen Nanostrukturen am Beispiel der reinen Au(100)-Oberflaeche und des selbstassemblierten Systems Sauerstoff auf Cu(110)

In this STM study, nanostructures on metallic single crystals are observed under UHV conditions. The aim of the work at the Au(100)-surface is to evaluate an energetic quantity, namely the step free energy, from a topographic structure information. Adatom and vacancy islands are produced on the tempered reconstructed Au(100)-surface by evaporation of submonolayer quantities of gold and sputtering with Argon ions, respectively. The decay of these islands is correlated with a decrease of the aspect ratio to approximately 1. After that the aspect ratio varies merely stochastically around this mean value. We could observe adatom islands at T=353 K, which neither grow nor decay over a long period of time and whose aspect ratio varies stochastically around the mean value of 1. In conclusion, we assume that these islands are in a thermodynamic equilibrium situation or at least close to it. By averaging over these island shapes, we obtain the equilibrium shape for this temperature. From island shape fluctuations we make a quantitative determination of the mean step free energy to 170 meV per atom. In completely separated experiments from the described ones above, the formation of the so-called (2 x 1) oxygen stripe phase on Cu(110) is imaged in situ, and simultaneously a quantitative determination of the induced surface stress is accomplished. (orig.)SIGLEAvailable from: http://deposit.ddb.de/cgi-bin/dokserv?idn=973322225 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman