Dresden 2009 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 51: Surface chemical reactions I
O 51.2: Vortrag
Donnerstag, 26. März 2009, 16:30–16:45, SCH A01
Real-space investigation of high-barrier diffusion of hydrogen on Si(001) — •M. Dürr1,2, C. H. Schwalb1, and U. Höfer1 — 1Fachbereich Physik und Zentrum für Materialwissenschaften, Philipps-Universität Marburg, D-35032 Marburg — 2Fakultät Angewandte Naturwissenschaften, Hochschule Esslingen, D-73728 Esslingen
Due to the strong corrugation of Si(001) with its dimer
row reconstruction, various diffusion channels exist already on the
flat, clean surface. Among the possible processes, diffusion between
two dimer rows is associated with the highest diffusion barrier; as
a consequence, it has not been observed by means of standard STM
experiments up to now.
To probe this high-barrier pathway in real space, we used a
combination of STM and nanosecond laser heating [1,2]. STM images
taken after different numbers of heating pulses represent snapshots
of the surface configurations frozen at various stages of the
diffusion process. In this way hydrogen diffusion associated with
rates as high as 108 s−1 could be monitored with atomic
resolution at 1400 K. We observe that diffusion across the dimer
rows is almost as effective as diffusion along the dimer rows. The
experiment thus demonstrates the importance of this high-barrier
process at elevated temperatures. Considering the large Si–Si
distance between the dimer rows, the observed diffusion rate is
surprisingly high. It is interpreted in terms of a strong concerted
movement of hydrogen and the Si lattice.
[1] M. Dürr et al., Science 296, 1838 (2002).
[2] C. H. Schwalb et al., Phys. Rev. B 75, 085439 (2007).