Probing high-barrier pathways of surface reactions by scanning tunneling microscopy

M. Dürr1,2, A. Biedermann1,3, Z. Hu1, U. Höfer2, T.F. Heinz1

1Departments of Physics and Electrical Engineering, Columbia University, New York, NY 10027, USA
2Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität Marburg, D-35032 Marburg, Germany
3Institut für Allgemeine Physik, Technische Universität Wien, A-1040 Wien, Austria

Science 296 (2002) 1838-1841

The ability of scanning tunneling microscopy to probe the pathways of thermally activated high-barrier surface processes is frequently limited by competing low-barrier processes that can confuse measurement of the true initial and final configuration. We introduce an approach to circumvent this difficulty by driving the surface process with nanosecond laser heating. The method is applied to determine the pathway of recombinative desorption in the H/Si(001) system. The observed configuration of dangling bonds after laser heating reveals that the desorbed hydrogen molecules are not formed on single dimers, but rather from neighboring silicon dimers via an interdimer reaction pathway.

Correspondence to: M. Dürr.

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