Reflectance and electroreflectance of TiO2single crystals. II. Assignment to electronic energy levels

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Abstract
For pt.I see ibid., vol.10, no.19, p.3893 (1977). The interband optical properties of TiO2are analysed on the basis of a tight-binding band structure which is calculated by using estimated values for the LCOAO parameters. The major interband transitions giving rise to the pronounced optical structure around 4 eV occur between energy band regions near the Sigma symmetry line of the Brillouin zone. The broad structure of the electroreflectance (ER) is mainly caused by the energy shift of these bands due to the dielectric polarisation. Values for four elements of the polarisation-potential tensor have been deduced from the experimental data which agree with the results of a quantitative model developed for the electro-optic effect. Some features of the ER fine structure are unambiguously identified as Franz-Keldysh oscillations and are designated to specific critical points.