Influence of high currents on atomic contacts

Abstract

In this thesis conductance measurements were performed on mechanically controlled single-atom contacts. Their behavior were studied at small local changes of the atomic configuration. For the manipulation of the metal atoms high electrical currents were applied, in order to stimulate discrete electromigration events. With alternating current directions single atoms were managed to reversibly switch back and forth. For each of the atomic configurations the individual quantum mechanical conductance channels could be identified using superconductivity. The known measuring method is based on the analysis of current-voltage characteristics in the regime of the so-called multiple Andreev reflections and on a numerical comparison to theory. The investigated aluminum atoms showed spectra of three characteristic channels in accordance to theoretical calculations. In statistical evaluations numerous contacts of different configurations are compared.