AVS 59th Annual International Symposium and Exhibition
    Surface Science Monday Sessions
       Session SS-MoM

Paper SS-MoM3
Probing Surface Chemical Reactions with Metal Nanofilm - Semiconductor Schottky Diodes

Monday, October 29, 2012, 9:00 am, Room 21

Session: Nonequillibrium and Nonlinear Processes
Presenter: I. Nedrygailov, University of Duisburg-Essen, Germany
Authors: I. Nedrygailov, University of Duisburg-Essen, Germany
E. Hasselbrink, University of Duisburg-Essen, Germany
D. Diesing, University of Duisburg-Essen, Germany
Correspondent: Click to Email
Most catalytic chemical reactions are complex processes, which include a variety of steps such as molecular and dissociative adsorption on a solid surface, interactions between intermediates, and desorption of products from the surface to the gas phase. Considerable effort has been made to achieve a detailed microscopic understanding of the dynamics of these processes using different experimental and theoretical methods, nevertheless still little is known about the routes of energy transfer accompanying the gas-surface interactions. As shown by McFarland, Nienhaus and coworkers, dissipation of chemical energy, released in catalytic reactions on metals, may proceed non-adiabatically by transferring a part of the energy into electronic degrees of freedom. This process is caused by a nonequilibrium state of the adsorbate surface complex and leads to the excitation of highly energetic (hot) electrons and holes in the metal surface. Detection of the excited charge carriers in metals is rather challenging because they relax within some 10 fs due to scattering processes (including electron and phonon pathways). A loophole is the use of metal nanofilm - semiconductor Schottky diodes. A ballistic transport of the excited charge carriers from the metal surface, where the excitation takes place, into the underlying semiconductor is possible in such diodes allowing for the direct detection of the hot electrons and holes as a chemicurrent. Detailed studies of chemicurrents can further our knowledge about the role of electronic and nuclear degrees of freedom in the dissipation of the chemical energy and thereby can give us a key for understanding of surface dynamics. In this contribution, we report on our methodology of nanofilm Pt-SiO2-Si Schottky diodes manufacturing and their application as detectors for chemically induced currents. We show experimental results with currents of up to several µA detected in the Pt-SiO2-Si diodes while the Pt top electrode is exposed to molecular hydrogen, oxygen or their mixtures with different molar ratios and a pressure in the range of 1 – 10 mbar. Thermal effects and electronic excitations in the Pt top electrode of Pt-SiO2-Si diodes, caused by the water formation reaction, are considered as possible sources of the observed currents.