Study Of Fabrciation And Properties Of ZnO Arrays Films

ZnO films have been attracting considerable attentions owing to their unique electrical and optical properties as well as promising applications in gas sensors, UV-light emitters and solar cells. The properties of ZnO nanostructure arrays can adjust by morphologies. Recently, morphology-controlled synthesis of multiple ZnO nanostructures and studying of the morphology-related properties have become hotspots in semiconductor field. Many methods have been used to prepare ZnO nanostructures, such as methal-organic chemical vapor deposition, vapor phase transport technique and liquid method. The physical methods require high temperature and complicated equipments. In contrast, the liquid method can be carried out in soft environments and lower energy consumption.In our experiments, zinc nitrate hexahydrate is used as starting material. The ZnO films are prepared on glass substrate and Si (100) by low-temperature wet chemical method and hydrothermal method, respectively. The influence of the process conditions on the morphological, structural, electrical and optical properties of ZnO films are investigated by X-ray diffraction, scanning electron microscope, standard four-point probe method, photoluminescence and field emission, respectively.The main findings are listed as follows:1) The influence of temperature and concentration on the structural and morphological of ZnO films are obvious.2) The cooling rate affects the optical and electrical properties of ZnO films dramatically. The ZnO film cooled at -15℃exhibits the lowest electrical resistivity of 0.525Ω·cm and the strongest photoluminescence in visible light. The increase of the conductivity and the enhancement of the photoluminescence are attributed to the increase of oxygen vacancies in the films.3) The films synthesized by hydrothermal method have absolute C-axis preferred orientation. The influences of seed layer, temperature, solution concentration, dopant concentration and pH value on the structural and morphological of ZnO films are obvious. When the dopant concentration is 5 at.%, part of the nanorods of the ZnO films become the nanotubes. The nanorods become nanoneedles at high pH value of 11.0. When the pH value increased to 11.7, the ZnO film becomes Zn2SiO4 film.4) The field emission of nanoneedles film is higher than nanorods film. The turn-on field for ZnO nanoneedles is found to be about 5.2 V·μm-1 at a current density of 10μA·cm-2. The emission current density from the ZnO nanoneedles reached 0.09 mA·m-2 at a bias field of 7.0 V·μm-1. The field enhancement factor of ZnO nanoneedles reached 1803.