Dresden 2011 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 30: Focussed session: Transparent conductive oxides II (jointly with HL, DS)

O 30.3: Topical Talk

Dienstag, 15. März 2011, 12:15–12:45, WIL B122

Optical properties of undoped and doped ZnO — •Axel Hoffmann and Markus R. Wagner — Institut für Festkörperphysik, TU Berlin, Hardenbergstr. 36, 10623 Berlin, Germany

A spectroscopic study of optical transitions and lattice dynamics of ZnO under the influence of external fields is reviewed. A comparative study of different ZnO single crystals and doped and undoped ZnO films reveals pronounced differences in the free and bound exciton luminescence which can be related to different impurity centers and strain levels. A correlation between the localization energies of excitons bound to the same chemical element in the neutral and ionized charge state is reported. The properties of the shallow impurity bound excitons are compared to defect related deeply bound excitons. The lattice dynamics of ZnO crystals are studied by Raman spectroscopy under the influence of external pressure. A variety of important material parameters is derived including high precision values of the hydrostatic pressure coefficients and Grüneisen parameters of all Raman active modes. For the Born transverse effective charge, an incorrect pressure dependence in the literature is discovered and revised. Raman measurements of ZnO single crystals under uniaxial pressure are reported. In combination with the hydrostatic pressure measurements on the same samples, the first experimental determination of the phonon deformation potentials of all Raman active modes in ZnO is achieved.