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O: Oberflächenphysik

O 10: Semiconductor surfaces and interfaces

O 10.8: Vortrag

Montag, 27. März 2006, 16:45–17:00, PHY C213

Sum-frequency generation study of hydrogen diffusion on vicinal Si(100) surfaces induced by resonant IR laser excitation — •Xu Han, Kristian Laß, and Eckart Hasselbrink — Fachbereich Chemie, Physikalische Chemie, Universität Duisburg-Essen, Universitätsstr. 5, D-45141 Essen

We report first measurements of a new way (non-thermal, non-electronic excitation) of inducing adatom diffusion. Under selective resonant excitation by tunable IR laser pulses, hydrogen diffusion between step sites or from step edges onto terraces of a vicinal Si(100) surface has been demonstrated. The state of the adsorbate has been monitored by means of IR-visible sum-frequency generation spectroscopy (using ps laser pulses). Hydrogen preferentially binds to the step edges on a Si(100) surface with D_B or S_B steps. For saturation coverage the stretch vibration of step-bonded monohydrides has been found at 2087 cm⁻¹, with a small blue shift at lower coverages. Hydrogen diffusion from D_B or S_B step edges to other weakly bonded sites at steps can be enhanced by resonant IR laser excitation at temperatures well below the threshold for thermally activated surface diffusion of hydrogen. Alternatively, hydrogen can also diffuse onto terraces, where the frequencies of isolated monohydride, monohydride with neighboring dihydride, and dihydride are 2100, 2104 and 2107 cm⁻¹, respectively, with a small red shift at lower coverages.