Hamburg 2001 – scientific programme
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O: Oberflächenphysik
O 25: Postersitzung (Grenzfl
äche fest-flüssig, Methodisches, Nanostrukturen, Organische Dünnschichten, Rastersondentechniken, reine Oberfl
ächen, Teilchen und Cluster, Zeitaufgelöste Spektroskopie, Sonstiges)
O 25.86: Poster
Wednesday, March 28, 2001, 15:00–18:00, Foyer zu B
Near surface phase transitions in 2H-NbSe2 and 2H-TaSe2 — •B. M. Murphy, M. Traving, J. Stettner, M. Tolan, and W. Press — Institut für Experimentelle und Angewandte Physik, Universität Kiel, D–24118 Kiel
Surface sensitive X-ray diffraction studies have shown, that the phase transitions in solid state materials are explicitly influenced by a spatial boundary (e.g. by a surface or a thin layer). Transition metal dichalcogenides like 2H-TaSe2 and 2H-NbSe2 show distinct 2-dimensional properties because of the weak van der Waals bonding between the layers. Therefore, it is interesting to study, if in the case of these layered materials the influence of the surface on the phase transitions is still observable. At low temperatures these crystals form charge density waves (CDWs) accompanied by a periodic lattice distortion. We investigated the phase transitions of 2H-TaSe2 and 2H-NbSe2 at TCbulk = 122.3 K and TCbulk = 33.5 K, respectively. At beamline BW2 (HASYLAB, Hamburg) Grazing Incidence Diffraction (GID) measurements have been performed at different incident angles to get data describing the surface behavior (αi=0.2o<αc) and the bulk behavior (αi=0.5o>αc).