Dresden 2014 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 30: Surface Chemical Reactions and Heterogeneous Catalysis II

O 30.8: Vortrag

Dienstag, 1. April 2014, 12:15–12:30, PHY C 213

Kinematic effects in the non-adiabatic energy dissipation during oxidation of Al surfaces — •Achim Gerstenberg, Ulrich Hagemann, and Hermann Nienhaus — University of Duisburg-Essen and Center for Nanointegration (CENIDE), Duisburg, Germany

There is a long-standing controversial debate on the nature of the low initial sticking of oxygen molecules on Al(111) surfaces [1]. In the present study, the reaction is investigated for low substrate temperatures with respect to the kinetic energies of the impinging oxygen molecules using the chemicurrent method. The released reaction energy is partly dissipated non-adiabatically by generation of electron-hole pairs in the metal surface. The created hot charge carriers are detected as a chemicurrent in large-area Al/p-Si (111) Schottky diodes with Al films of 4 to 20 nm thickness. The homogeneous Schottky barrier height is determined to be 0.45 eV. Upon exposure to a hyperthermal molecular beam of oxygen molecules seeded in He gas the temporal evolution of the chemicurrent exhibits a maximum in agreement with the low initial reaction probability and in accordance to a nucleation and growth kinetics. When the kinetic energy of the molecules is raised from 50 to 250 meV the respective chemicurrent increases strongly. This kinematic current enhancement is still observed after longer exposures for the partially oxidized Al(111) surface.

[1] M.Kurahashi and Y.Yamauchi, PRL 110 (2013) 246102 and ref. therein.