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HL: Fachverband Halbleiterphysik

HL 39: ZnO and Relatives II

HL 39.1: Talk

Tuesday, March 27, 2012, 11:30–11:45, EW 202

A DFT study of N impurities in ZnO nanoparticles — •Johann Gutjahr, Sung Sakong, and Peter Kratzer — Fakultät für Physik and Center for Nanointegration (CeNIDE), Universität Duisburg-Essen, Duisburg, Germany

Zinc oxide nanostructures have attracted increasing interest due to their promising applications in electronic devices. ZnO is possibly ideally suited for blue/UV light-emitting diodes or laser diodes, once n- and p-doped ZnO can be produced reliably and reproducably. Nevertheless, p-type ZnO was obtained experimentally by N doping (Nature Materials 4,42(2005)). We study N doping of nanoparticles (NP) because their properties can be tuned and they offer a simple way to produce ZnO material by e.g. sintering. In bulk ZnO, DFT calculations show the deep character of the N impurity on the O site because of the too high position of the charge transfer level (0/−) in the band gap (APL 95,252105(2009)).

As expected, the NP HOMO-LUMO gap is increased with decreasing NP size, but the N defect formation energy is found to be similar to bulk ZnO. Moreover, from the change of electron affinity we conclude the deepness of the N acceptor level. We also study different kinds of passivation and find that with H-passivation the adsorbate-induced states lie between VBM and acceptor level. Based on this, we explore the N acceptor level in thin ZnO-films as a model for the surface of a bigger particle to learn more about the influence of H-induced states.