Photoluminescence And Field Emission Of Oxide Nanomaterial

Nanomaterials and nanostructures have received great interests due to their peculiar and fascinating properties, such as surface effect, small size effect and quantum effect, superior to their bulk counterparts for application. Because of the unique quality of photoluminescence and field emission, nanooxides have received great attention. Besides, ZnO is the material, which has the most abundant nanostructure.This thesis reported that we had prepared ytterbia and zinc oxide nanocrystals which were doped with lithium and zinc oxide nanotube respectively, and conducted studies on nanocrystals upconversion and zinc oxide field emission properties. The main studies are:Ytterbia and zinc oxide nanocrystals doped with erbium were prepared by precursor method. X-ray diffraction (XRD) indicated that the structures of two kinds of nanocrystals were cubic and wurtzite respectively. A diode laser emitting at 976 run wavelength was used to irradiate the NC, and upconversion photoluminescence phenomenon was discovered. The upconversion photoluminescence spectra indicated that the intensity of the specimen doped with lithium was stronger than the one without lithium ions, because the diffusion of lithium ions altered the symmetry of the crystal field around erbium. As to ytterbia, after study the relation between the irradiation power and the upconversion photoluminescence, we got the conclusion: at low excitation power, it should be a two-photon mechanism, and when pumping power exceed the threshold 110 mW, it should be generated through avalanche photon absorption.ZnO nanotubes array were obtained by hydrothermal method on the silicon wafer which was substrate. And then the field emission properties were measured to research field emission enhancement factor when the ZnO was the cathode. It was found that Znonanotubes have excellent field emission properties, with the threshold field of 5.7 V/μm.In order to decrease the screen effect, and make the total electric current large, the value of the density of the emitter should be in the proper range.