Abstract
nO is of considerable interest for optoelectronic device applications dueto its wide band gap and high exciton binding energy. In spite of decadesof study and recent progress in research on ZnO properties, there remainedunresolved controversies which are mainly related to native defects formedduring crystal growth. Positron annihilation spectroscopy (PAS) is amongthe methods to tackle this structural issue. ZnO nanostructures, like e.g.nanorods and tetrapods, are of special interest for device applications.However, their characterization remains an ongoing challenge. This talkintends to review our recent efforts and latest achievements in thisdirection. Results obtained will comprise PAS in the form of Slow PositronImplantation Spectroscopy (SPIS) and Pulsed Low Energy Positron LifetimeSpectroscopy (PLEPS), Nuclear Reaction Analysis (NRA), Atomic ForceMicroscopy (AFM), conductive AFM (C-AFM), Nuclear Magnetic Resonance(NMR), Electron Spin Resonance (ESR), Photoluminescence (PL) spectroscopy,and latest theoretical investigations of structure-related and positronproperties of selected defects. The fundamental importance of arelationship between fabrication conditions, native defect formation, andresulting optical and electronic properties is demonstrated by gettingeither inferior (nanorods) or significantly improved (tetrapods) opticalproperties compared to single crystal samples, depending on thenanostructure fabrication method.
