Co掺杂纳米ZnO微结构的正电子湮没研究

摘要

ZnO nanopowders are mechanically mixed with a certain quantity of Co3O4 nanopowders to obtain 10at.% Co doped Co3O4/ZnO composites.The nanocomposites are annealed in argon atmosphere at different temperatures between 100 ℃ and 1200 ℃.The structure and the grain size of the nanocomposite are investigated by X-ray diffraction 2θ scans.With annealing temperature increasing up to 700 ℃,Co3O4 phase gradually disappears,and ZnO grain size begins to increase significantly.After annealing at above 1000 ℃,Co3O4 phase completely disappears,and CoO phase（rock-salt crystal structure） appears.Positron annihilation lifetime measurements reveal a large number of Zn vacancies and vacancy clusters existing in the interface region of the Co3O4 /ZnO nanocomposites.These defects are gradually recovered after annealing at above 700 ℃,and their number is under the detection limit after annealing at 900 ℃.The same conclusion can be drawn from the coincidence Doppler broadening（CDB） measurements.%利用正电子湮没技术研究了10at.%Co掺杂的Co3O4/ZnO纳米复合物中退火对缺陷的影响.利用X射线衍射（XRD）测量了Co3O4/ZnO纳米复合物的结构和晶粒尺寸.随着退火温度升高,Co3O4相逐步消失,ZnO晶粒尺寸也有显著增加.经过1000℃以上退火后,Co3O4相完全消失,并出现了CoO的岩盐结构.正电子湮没寿命测量显示出Co3O4/ZnO纳米复合物中存在大量的Zn空位和空位团.这些空位缺陷可能存在于纳米复合物的界面区域.当退火温度达到700℃后Zn空位开始恢复,空位团也开始收缩.900℃以上退火后,所有空位缺陷基本消失,正电子寿命接近ZnO完整晶格中的体态寿命值.符合多普勒展宽谱测量也显示Co3O4/ZnO纳米复合物经过900℃以上退火后电子动量分布与单晶ZnO基本一致,表明界面缺陷经过退火后得到消除.