Berlin 2008 – scientific programme

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O: Fachverband Oberflächenphysik

O 93: Surface Chemical Reactions

O 93.5: Talk

Friday, February 29, 2008, 11:15–11:30, MA 043

Internal exoemission in K/p-Si(001) Schottky diodes — •Kornelia Huba, David Krix, and Hermann Nienhaus — Fachbereich Physik, Universität Duisburg-Essen, Duisburg

Ultrathin potassium films of typically 1 nm thickness were deposited on hydrogen terminated p-Si(001) surfaces at low temperatures. Using a softly approached gold ball, an electric contact to the thin film was formed and current/voltage characteristics were recorded as a function of the substrate temperature. The K/p-Si contacts are Schottky diodes with low reverse currents of below 10 pA. Applying thermionic emission theory a homogeneous Schottky barrier height of 0.56 eV was determined. Oxidation of the K films by exposures to molecular oxygen leads to chemically induced electronic excitations. They were studied by measuring the internal exoemission currents, i.e. chemicurrents, in the diodes. The chemicurrent transients exhibit a maximum and less significant additional features after longer exposures. In addition to the current measurements, the oxygen uptake as well as the K film thickness and morphology were characterized by Auger electron spectroscopy and Kelvin probe measurements.