Regensburg 2007 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 17: Hydrogen in materials
MM 17.3: Vortrag
Dienstag, 27. März 2007, 10:45–11:00, H6
Temperature dependent FT-IR-spectroscopy on YH3 — •Stefan Weber and Joachim Schoenes — Institut für Physik der Kondensierten Materie, TU Braunschweig
Thin films of yttrium metal have become known under the term of switchable mirrors. Upon hydrogen loading the metallic films undergo a metal to insulator transition, e.g. the opaque metallic films become transparent semiconductors.
Recent Raman studies [1] showed that YH3−δ behaves like a doped semiconductor which results in an unusual strong temperature dependence of one particular phonon due to electron-phonon interactions. Fourier-transform-infrared-spectroscopy show peaks that can be attributed to hydrogen vibrations by comparison of samples loaded with either hydrogen or deuterium. One of the apparent phonons displays a much stronger temperature dependence than the others. A careful study of the line shapes of deuterium loaded samples reveals a shoulder which can be attributed to an electronic transition between a donor level and the conduction band of YH3−δ. In hydrogen loaded samples this electronic transition coincides with a phonon which hampers its clear identification. But as it doesn’t underlay the isotope shift our additional data confirm the assignment of that spectral structure to an electronic transition. This result supports the model of strong correlations in the electronic structure of YH3−δ [2].
[1] A.-M. Racu and J. Schoenes, Phys. Rev. Lett. 96, 017401 (2006)
[2] K. K. Ng et al., Phys. Rev. B 59, 5398 (1999)