Influence of the free carrier concentration on the optical properties of SnO2 in rutile structure
Christian Lidig (Institut für Experimentelle Physik, Otto-von-Guericke-Universität Magdeburg)

Semiconducting metal oxides such as rutile SnO2 have attracted much interest in recent years.
High-quality bulk crystals and single crystalline heteroepitaxial films, covering a wide range of free electron concentrations, became available allowing the determination of intrinsic optical properties as well as related fundamental band-structure parameters.
The components of the dielectric tensor where measured with spectroscopic ellipsometry from the infrared (IR) into the vacuum-ultraviolet (VUV) spectral region. The analysis of the IR dielectric function yields to the phonon frequencies and the coupled phonon-plasmon-modes from which the e?ective electron mass as a function of the carrier density is obtained. Many-body e?ects such as band-gap renormalization and band filling have a strong impact on the behaviour around the fundamental band gaps, a quantitative description of these properties will be presented.
Finally synchrotron-based studies in VUV provide the transition energies related to critical points of the band structure. The synchrotron-based studies will compared to recent theoretical calculations.
It turns out that electron-hole interaction influences the dielectric function up to 20 eV resulting in a pronounced redshift and redistribution of the oscillator strength of features related to van Hove singularities.