ZnO has been attractive material for potential applications, for example, lasers and optoelectronic devices. The excitonic luminescence with decay times in ps range will be observed up to room temperature. It is expected high quantum yield for fast luminescence due to exciton quantum size effects on nanostructured ZnO. The ZnO nanocrystals and thin films were synthesized and characterized by FTIR, x-ray diffraction and SEM methods. The luminescence spectra and decay kinetics were studied under pulsed laser (266 nm, 2 ns) and pulse electron beam (10 ns 250 keV) excitation. Nanocrystalline powders with controlled grain size 10-40 nm was prepared by microwave driven hydrothermal process using different chemical reactions. Nanostructured ZnO thin films were prepared using i) dc magnetron sputtering technique in mixed Ar/O2 atmosphere from metallic zinc target on Si substrates. After deposition, the samples were heat treated at about 1000C for one hour. Thus obtained films had thickness of about 500 nm and were not preferentially oriented, according to XRD; ii) on Si substrates using atmospheric pressure chemical vapor deposition (APCVD) starting from a mixture of ZnO and graphite powders. Such films had larger thickness of about few microns and were oriented along c-axis in (002) direction.
The photoluminescence spectra of nanopowders and both types of films consist of broad defect band at 1.9-2.4 eV region and excitonic luminescence band at about 3.2 eV. The decay kinetics had complex structure with more than two exponent.