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DS: Dünne Schichten
DS 38: Postersitzung
DS 38.44: Poster
Dienstag, 28. März 2000, 09:30–17:30, Poster B
Determination of the optical constants of YHx (x=2,3) by spectroscopic ellipsometry. — •M. Broschwitz, U. Barkow, A. Jacob, A. Borgschulte, and J. Schoenes — Institut für Halbleiterphysik und Optik, TU Braunschweig
Recently rare earth hydride thin films have attracted
great interest
due to the metal-insulator transition between the dihydride and the
trihydride phase[1]. Therefore the optical
constants as well as the transmission and reflectivity change dramatically
between these two states. As the oxides
of rare earth metals prevent the loading with hydrogen, a protective layer
of palladium of about 20 nm has to be
deposited, which will influence the optical behaviour seriously.
Yttrium films were loaded in situ with hydrogen under different partial
pressures to form both YH2 and
YH3. These samples are capped with CaF2 layers, which prevent
oxydation and hydrogen diffusion. The optical
properties have been investigated by a laboratory ellipsometer in the range
of 1 to 4 eV. A least square fit using
a coherent matrix formalism leads to a determination of the refractive
index and the extinction coefficient.
Additionally, transmission and reflection measurements were done in the
spectral range from 1 to 6 eV.
[1] J. N. Huiberts et al., Nature 380, 231 (1996)