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HL: Fachverband Halbleiterphysik

HL 60: Poster II: Optical Properties, incl. Photonic Crystals and Ultrafast Phenomena

HL 60.18: Poster

Donnerstag, 25. März 2010, 18:00–20:00, Poster D1

Low-temperature dielectric function of a-plane Mg_xZn_1−xO — •David Schumacher, Rüdiger Schmidt-Grund, Philipp Kühne, Helena Hilmer, Holger Hochmuth, and Marius Grundmann — Universität Leipzig, Fakultät für Physik und Geowissenschaften, Institut für Experimentelle Physik II, Linnéstr. 5, 04103 Leipzig, Germany

The object of our investigation is the temperature dependent dielectric function of Mg_xZn_1−xO (x < 0.1) thin films. It has been obtained by means of spectroscopic ellipsometry in the energy range of 1 - 4.5 eV and at temperatures between 10 K and 470 K. The a-oriented Mg_xZn_1−xO thin films were deposited by pulsed laser deposition (PLD) on r-oriented sapphire (Al₂O₃) substrate. All measurements were performed under UHV conditions (p < 10⁻⁹ mbar) in order to prevent an accumulation of ice and residual gases on the sample surface. Since previous experiments had shown a degradation of the surface quality due to the high-temperature measurements under UHV conditions, all samples were passivated by an amorphous 60 nm thick YSZ (Yttria-stabilized zirconia) layer.

The independent components of the dielectric tensor parallel ε_∥ and perpendicular ε_⊥ to the crystal axis were found by layer stack model analysis using parameterized model dielectric functions. We derived the temperature and alloy dependence of the near band gap band-to-band transition energies, exciton binding energies and broadening parameters.