Research On Photoluminescence And Raman Scatter Of Low-dimensional ZnO Structures

Zinc oxide (ZnO) as a kind of ultraviolet (UV) emission semiconductor materials hasattracted considerable research attention in recent years, especially for the low-dimensionalstructure of ZnO. In low-dimensional structures, charged carriers are confined to certainenergy levels, enhancing exciton oscillator strength and light-emitting efficiency. When theoscillator strength is large enough, nonlinear effects can be observed even underlow-excitation level, so the lasing threshold decreases. The research on optical and structuralproperties of low-dimensional ZnO structure will make the ZnO material into application. In present work, the photoluminescence (PL) and Raman spectra were discussed in threeaspects: 1. The multiphonon resonance Raman specra of ZnO nanocrystals embed in metal Zn thinfilm were investigated. As in other alloy structures like ZnOnX1-n, the PL spectra showsmultiphonon Raman signal imposed on the low intensity PL background. To explain thesesphenomena, a structural model was put forward. In this model the affect of interfacialproperties of Zn-ZnO were considered. And the build-in electric field induced byheterogeneous junction enhances the resonance Raman and quenches the PL. 2. Consequently, a new method to characterize the growth orientation of thelow-dimension ZnO structure was put forward basing on the study of polar band. This methodcan also be used to measure orientation distribution of ZnO one-dimension structurequantitatively. To screen the effect the disturbance of internal elementary excitation andsubstrate, it is necessary that the Raman scatter experiment be taken under the resonancecondition. The method was also been compared with other character methods. 3. Low-dimensional (nanowalls) ZnO structures were prepared by a two-step growthmethod with oxygen-plasma-assisted molecular beam epitaxial (P-MBE), where the as-grownfilm was first engraved to a porous template by the oxygen plasma, then the ZnO nanowallswere grown on the template. The resonance Raman spectra showed the surface mode. Amorphology model was proposed basing on the scanning electron microscopy patterns andthis mode. Room- and low-temperature photoluminescence (PL) showed the nanowalls hadintense ultraviolet emission properties, which profited from the low-dimensional structurewith few defects.