Dresden 2011 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 87: ZnO: Growth and Defects

HL 87.10: Talk

Friday, March 18, 2011, 12:45–13:00, POT 51

Strain distribution in ZnO microwires — •Christof P. Dietrich, Martin Lange, Fabian J. Klüpfel, Rüdiger Schmidt-Grund, Holger von Wenckstern, and Marius Grundmann — Universität Leipzig, Abteilung Halbleiterphysik, Institut für ExperimentellePhysik II, 04103 Leipzig, Germany

We present a direct experiment to determine the strain dependence of semiconductor energy bands with high precision. For this purpose we benefit from the unique properties of self-organized grown ZnO microwires with respect to their excellent crystal quality and the possibility to easily adjust the strain in such objects by bending, opposite to thin films or bulk single crystals. In order to study the band gap energy variation with strain we measure the related photoluminescence (PL) of the exciton recombination spatially resolved at low temperatures on mechanically bent ZnO microwires fabricated by carbothermal reduction. We show that mechanical bending leads to a significant blue and red-shift of the wire luminescence due to the formation of compressive and tensile strained parts of the wire, respectively. Linescans perpendicular to the wire axis showed maximum energetic shifts of the dominant recombination peaks of ±30 meV due to strain values of ±1.5 %. The compressive and tensile strain inside the wires turned out to be symmetrically distributed perpendicular to the wire axis meaning that the neutral fibre coincides with the central wire axis. From these experiments, we are able to precisely determine the deformation parameter that connects the energetic shift of the wire luminescence and the applied uniaxial stress.