Regensburg 2002 – wissenschaftliches Programm
M 26.21: Poster
Donnerstag, 14. März 2002, 14:30–16:30, Saal C
Raman spectroscopy on YHx thin films — •A.M. Carsteanu, H. Kierey, M. Rode, A. Borgschulte, and J. Schoenes — Institut f"ur Halbleiterphysik und Optik, Technische Universit"at Braunschweig, Mendelssohnstr. 3, 38106 Braunschweig
In the hydrogenation process of an Y film, three different phases are involved. The starting point is the metallic hcp phase of Y, where hydrogen can exist only in solid solution (α phase). Above a hydrogen content of x=0.23 in YHx the α phase coexists with a fcc-based, still metallic β phase. The β phase is stable between x=1.8 and 2.1. Above x=2.1 a hexagonal γ phase starts to form. A metal insulator transition occurs for x≈2.75. Raman spectroscopy is a useful tool to differentiate between the three phases. The low temperature measurements together with polarisation resolved and angular dependent measurements helped us to determine, in addition to the γ phase , the β phase phonon, which corresponds to the CaF2-like structure. The measurements were performed on an inhomogeneous sample, where the three phases coexist. The space resolved Raman spectra display a region where the dihydride and trihydride phases mix, which corresponds to a transition domain in the optical microscope image. The temperature dependence of the position and FWHM of each line is also discussed.
 H. Kierey et. al., Phys. Rev. B 63, 134109 (2001)