Karpyna V. Structure and properties of ZnO films and nanoformations grown by different methods

Dissertation is devoted to the study of deposition processes of zinc oxide thin film growth by thermal reaction methods and magnetron sputtering, creating solid solutions Zn1-хCoхO and growing ZnO nanostructures with the aim of creation the light emitting devices for a ultraviolet range, new materials for spintronics and cold cathodes for vacuum microelectronics on their basis. The structure and surface morphology of undoped ZnO films and nanostructures, their photoluminescence excited by continuous and pulsed lasers was investigated; structure, optical and magnetic properties of solid solutions Zn1-хCoхO and electron field emission from thin films and nanostructures ZnO was investigated too. As a result of the research the peculiarity of photoluminescence of zinc oxide films and nanostructures was studied. In particular, it was shown that a clear exciton photoluminescence is observed in annealed films with perfect crystal structure. The influence of film texture and nature of substrate on the photoluminescence spectra was investigated. The photoluminescence mechanisms of ZnO films was studied at low temperatures and was found that the band at 3.32 eV, which is often observed in the photoluminescence spectra is caused by structural defects. At exciting with powerful pulsed laser the stimulated UV PL is observed at the recombination of free excitons included their phonon replicas as well as exciton-electron interaction. In dissertation work the conditions for the formation of Zn1-хCoхO solid solutions was studied and was found that solid solutions are paramagnetic within the solubility limit of cobalt in zinc oxide. For the first time, it was found by X-ray absorption spectroscopy that the cobalt in solid solutions Zn1-хCoхO has other charge state 3+, which indirectly proves the formation of precipitates phases of cobalt oxide nanoclusters responsible for the antiferromagnetic interaction. In dissertation the emission properties of zinc oxide nanostructures and nanostructured gallium-doped ZnO films, was evaluated compared with traditional silicon cold cathodes. The influence of surface morphology on the emission properties of ZnO nanostructures was investigated.