Characterization of indirect and direct interband transitions of anatase TiO2 by thermoreflectance spectroscopy

We characterize three as-deposited anatase TiO2(a-TiO2) films with different deposition flux angles of 0 S, 53 S, and 86 S tilted to Si < 001 > using thermoreflectance (TR) measurement in the temperature range between 30 and 300 K. The TR spectra at low temperature clearly show considerable difference in interband transitions of the tetragonal a-TiO2 with the largely top plane of {001} or the largely side planes of {100} and {010}. The indirect and direct interband transitions of the a-TiO2 are evaluated. The temperature dependences of the interband transition energies of the a-TiO2 are analyzed. The optical-axial anisotropy of the a-TiO2 films is discussed. (C) 2008 American Institute of Physics.