Electronic Structure of Ti2O3 from Single Crystal Thermoreflectance Spectroscopy

Abstract
For the first time studies are made of the polarized thermoreflectance of an oriented Ti2O3 single crystal. The spectra in the photon energy range 1 to 3.5 eV are taken at room and liquid nitrogen temperature. Optical transitions involving the 3d electrons, which play a crucial role in the semiconductor‐to‐metal transition, are studied. The optical transition at 2.9 eV is identified as a transition at a M2 critical point by Kramers‐Kronig analysis of the thermoreflectance spectra. A clear evidence of a plasmon excitation at 1.82 eV in the semiconducting Ti2O3 is reported. The temperature shift of the bands is in agreement with the band‐crossing model of the semiconductor‐to‐metal phase transition.

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