Berlin 2005 – wissenschaftliches Programm
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M: Metallphysik
M 4: Wasserstoff in Metallen
M 4.4: Vortrag
Freitag, 4. März 2005, 11:15–11:30, TU H2038
Lattice distortions in β-YH2+δ and cubic YH3 thin films studied by Raman spectroscopy. — •A.-M. Racu1, M. Rode1, D. Zur1, A. Borgschulte2, R. Westerwaal2, and J. Schoenes1 — 1Institut für Halbleiterphysik und Optik, TU Braunschweig, Mendelssohnstrasse 3, 38106 Braunschweig, Germany — 2Division of Physics and Astronomy, Faculty of Sciences, Vrije Universiteit, De Boelelaan 1081, Amsterdam, The Netherlands
We have monitored with Raman spectroscopy the metal insulator transition of Y films grown on (111) CaF2 substrates and capped with Pd. The γ phase (YH3) has a hexagonal structure characterized by a Raman spectrum with nine lines at room temperature. The stoichiometric β phase (YH2) is cubic and shows only one line. In the superstoichiometric β phase of YH2+δ we find changes in the spectra which are not compatible with a cubic lattice. There are clear indications that the cubic lattice is distorted into a tetragonal structure in YH2+δ. The Raman mapping image during unloading of an Y film shows a regime of coexistence between the γ and the superstoichiometric β phase. The results are compared with measurements on MgzY1−zHx which also show a distortion of the cubic lattice.