Thermal evolution of defects in as-grown and electron-irradiated ZnO studied by positron annihilation
Thermal evolution of defects in as-grown and electron-irradiated ZnO studied by positron annihilation
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DOI：
10.1103/physrevb.75.245206
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发表时间：
2007-06
影响因子：
3.7
通讯作者：
Z. Q. Chen;Shao-jie Wang;M. Maekawa;A. Kawasuso;H. Naramoto;Xiao-li Yuan;T. Sekiguchi
中科院分区：
文献类型：
--
作者：
Z. Q. Chen;Shao-jie Wang;M. Maekawa;A. Kawasuso;H. Naramoto;Xiao-li Yuan;T. Sekiguchi
用正电子湮没谱研究了ZnO单晶中的空位型缺陷。生长缺陷被认为是与锌空位（VZn）相关的缺陷，并且可以通过高于600 °C的退火容易地去除。当受到3 MeV电子辐照，剂量为5.5×1018 cm−2时，也会在ZnO中引入VZn相关的缺陷。这些辐照诱导的VZn中的大多数在低于200 °C的温度下通过与接近的金属复合而退火。然而，在约400 °C下退火后，产生二次缺陷。多普勒展宽测量的详细分析表明，辐照引入的缺陷和退火引起的二次缺陷属于不同的物种。这两种缺陷对正电子的俘获具有不同的温度依赖性。结合拉曼散射的研究，初步讨论了可能的候选人的二次缺陷。在700 °C下退火后，所有空位缺陷被退火除去。阴极发光测量表明，VZn是不相关的可见光发射在2.3 eV的ZnO，而是作为非辐射复合中心。
Vacancy-type defects in as-grown ZnO single crystals have been identified using positron annihilation spectroscopy. The grown-in defects are supposed to be zinc vacancy (VZn)-related defects, and can be easily removed by annealing above 600 °C. VZn-related defects are also introduced in ZnO when subjected to 3 MeV electron irradiation with a dose of 5.5×1018 cm−2. Most of these irradiation-induced VZn are annealed at temperatures below 200 °C through recombination with the close interstitials. However, after annealing at around 400 °C, secondary defects are generated. A detailed analysis of the Doppler broadening measurements indicates that the irradiation introduced defects and the annealing induced secondary defects belong to different species. It is also found that positron trapping by these two defects has different temperature dependences. The probable candidates for the secondary defects are tentatively discussed in combination with Raman scattering studies. After annealing at 700 °C, all the vacancy defects are annealed out. Cathodoluminescence measurements show that VZn is not related to the visible emission at 2.3 eV in ZnO, but would rather act as nonradiative recombination centers.