Preparation And Photoluminescence Of ZnO Nanobul Array

Owing to the fine electical and optical properties, together with the simple synthesize method, Zinc oxide have aroused much attention in the photoelectron area at home and abroad, espercially the one dimensional(1D) ZnO nanostructure.ZnO nanostucture has high light emitting efficiency in ultra-violet(UV) waveband at room temperature and low threshold as for simulated emission, which is an ideal material for UV light emitting devices including UV lasers. Well-aligned1D ZnO nanostructure can be used as working electrode in solar cells because it can separate electron-hole pairs sharply and be a ideal channel for transmitting electrons.This thesis took ZnO nanorods as the subject based on successfully prepared well-aligned ZnO nanorod array(NRA) through a two-process hydrothermal method. We further studyed lasing characteristics of ZnO NRA. At last, we prepared ZnO/CdS and ZnO/ZnSe composite structrues. The thesis is mainly divided into three sections.In the first section, we inverstigated the factors that could controll the growth of ZnO nanorods, including ZnO seed layer buffering the lattice dismatch between ZnO and Si substrate, the selection of the zinc salt to react with hexamethy-lenetetramine (HMT) and the growth conditions in hydrothermal process. Results show that the ZnO nanorods reacted by mixed solution of Zn(NO3)2·6H2O and HMT have higher aspect ratio and emitting efficiency compared with ZnCl2and HMT. The ECR-PLD deposited ZnO seed layer can buffer the dismatch between ZnO and Si substrate, assist and induce the ZnO nanorods growing with the preference of perpendicular to substrate. The growth of ZnO nanorods also affected by the grain size and thickness of ZnO seed layer. The best pre-annealing temperature and thickness of ZnO seed layer are400℃and20nm, respectively. The optimal hydrothermal concentration, temperature and time are0.04M,90℃and6hours respectively.The lasing characteristics of ZnO NRAs is presented in the second section, on the basis of surface morphology examination, structural characterization and annealing. The prepared ZnO NRAs have c-axis oriented wurtzite structure,46nm mean-sized crystallites, a typical diameter of30to70nm and length of1.1μm and are nearly aligned. The properties of light emission were studied by continuous wave and30ps pulsed ultraviolet excitation. At room temperature, the ZnO NRAs are capable of emitting strong PL and pulsed stimulated emission, with the latter showing obvious lasing characteristics. The threshold power density for lasing was observed to be-16kW/cm2. The excellent UV light emmision attributed to well-alligned ZnO NRA with high crystal quality.The third section used the pulsed laser deposition to fabricate the ZnO/CdS and ZnO/ZnSe composite structrues on the basis of well-alligned ZnO NRA. The surface morphology, optical properties and crystal structural results show that the stability of ZnO/ZnSe composite structrue is higher than ZnO/CdS. At the same deposition condition, ZnSe nanoparticle can cover the deeper length of ZnO nanorod compared with CdS. We caculated the average size of CdS and ZnSe nanoparticle on composite stuctures, which are22.7and16.3nm, respectively. The PL of both composite stuctures have lower UV emission peak and lower defect emission band.