Research On One-dimensional Nanostructured ZnO Doped By Eu And Li

ZnO is a II-VI wide direct-gap (3.37eV) semiconductor with large exciton binding energy of60meV at room temperature. It has extensive perspective of development in semiconductor light-emitting devices, semiconductor lasers, UV detectors and so on. Moreover, nano-ZnO has become a research focus in recent years because of its unique superior properties derived from the limitation in dimension and scale.At present, doping is the main means used to modificate and tailor the energy gap of ZnO to obtian high efficient homoj unction or heteroj unction light-emitting devices. This paper mainly studied ZnO:Eu and ZnO:Li1-D hybrid nano-materials which were synthesised via combustion method with post annealing. Performance tests had been made as well. The main results are as follows:ZnO:Eu hybrid materials:1. In the sample calcined at600℃, Eu(Ⅲ) and ZnO formed supersaturated solid solution in which a shallow donor level was contructed. The UV emission was increased while the native defect emission was inhibited because of the existence of this impurity level. In addition, the auger effect and fano effect caused by doping Eu(Ⅲ) could also influence the luminescent properties of the samples.2. In the sample calcined at1000℃, Eu(Ⅲ) precipitated from the main structure and aggregated on ZnO (0001) crystal face in the form of Eu2O3. Intrinsic emission from the excitation state of ZnO could excitate the above Eu2O3effectively. Thus, the luminescence of4f electrons could be obtained by secondary excitation.ZnO:Li hybrid materials:1. The sample calcined at600℃was interstitial solid solution structure. Li(I) formed a deep donor level and a shallow donor level in energy gap. The UV emission was increased while the green emission associated with the deep donor level was inhibited because of the existence of the shallow donor level.2. The sample calcined at1000℃was substitutional solid solution structure. The ionic substitution of Li for Zn caused the contraction of the crystal structure with an obvious shortening in c axis direction. Li(I) provided a shallow acceptor level in the main energy gap and also provided a deep donor level as the sample calcined at600℃. Two UV emission peaks at similar wave length appeared in the excitation spectrum because of the existence of the shallow acceptor level. In addition,The electronic transitions from the deep donor level to the shallow acceptor level could provide convenience for green emission. Therefore, strong green emission peaks were obtained.