Berlin 2008 – scientific programme
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O: Fachverband Oberflächenphysik
O 93: Surface Chemical Reactions
O 93.6: Talk
Friday, February 29, 2008, 11:30–11:45, MA 043
Non-adiabatic Phenomena during Oxidation of K/Pd-Thin-Films on Silicon — •David Krix, Kornelia Huba, and Hermann Nienhaus — Fachbereich Physik, Universität Duisburg-Essen, Duisburg
Large area, nanometer thick Pd films were grown on silicon substrates. On H-terminated, Boron doped H:p-Si(001) surfaces a Schottky barrier height of Φp = 0.38 eV could be extracted from I-V-measurements using thermionic emission theory. With nearly ideal behavior the diodes show reverse currents of below 1 nA at low temperatures of 120 K. Applying small amounts of K to the surface makes it highly sensitive to oxidizing gases. Similar to exoemission experiments, hot charge carriers are produced during oxygen exposure which can be measured as a chemicurrent, i.e. internal exoemission, flowing in a circuit involving the Schottky diode as a sensor.
Sensor parameters like K coverage and Pd film thickness were modified to study their influence on the time resolved chemicurrent transients. The total chemicurrent yield, i.e. the total amount of charge detected, was found to be exponentially attenuated with increasing Pd thickness at a constant value of λ ≈ 1.1 nm. Auger emission spectroscopy and Kelvin probe measurements were used to compare the evolution of the chemicurrents to the oxygen uptake of the samples.