Regensburg 2000 – wissenschaftliches Programm
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O: Oberflächenphysik
O 11: Postersession (Eröffnung)
O 11.131: Poster
Montag, 27. März 2000, 19:00–22:00, Bereich C
Solving the phase problem in surface crystallography: Umweganregung via a bulk reflection — •B. Jenichen1, V. Kaganer1, M. Albrecht2, A. Hirnet2, M. Gierer2, W. Moritz2, and K.H. Ploog1 — 1Paul-Drude-Institut für Festkörperelektronik, Hausvogteiplatz 5-7, D-10117 Berlin — 2Institut für Kristallographie der Universität München, Theresienstrasse 41, D-80333 München
For surface x-ray diffraction the experimental determination of phases is possible by simultaneously exciting a surface and a bulk reflection at grazing incidence. In the three beam case the amplitude of the directly diffracted wave is proportional to the sum of the amplitudes of the incident and the specularly reflected waves whereas the amplitude of the Umweg wave is proportional to that of the bulk diffracted wave. This interference between surface reflections excited by the incident and the bulk diffracted waves has been observed at the Ge(113)−(3×1) reconstructed surface. The experimentally determined phases are compared to the phases resulting from the known surface structure and the interference of the direct and the Umweg waves. The three beam diffraction condition can be found for a sufficient large number of surface reflections so that the method may serve as a starting point for structure determination by direct methods.