Abstract Lithium-indium di-selenide (LiInSe2) is a semiconductor material, which has been shown promising for applications in nonlinear optics and neutron detection. LiInSe2 crystals of optical quality, of different (from greenish to red) color were grown. Analysis of the fundamental absorption edge shows allowed direct band-to-band transitions and reveals structural disorder leading to the blurring of the edges of valence and conduction bands. Photoluminescence (PL) intensity is low in LiInSe2 of stoichiometric composition and increases after sample annealing in Se vapors. A narrow line at 408 nm is associated with free excitons. Analysis of PL and PL excitation spectra allows one to associate broad emission bands with point defects as well as with self-trapped excitons. The mean positron lifetime increases after annealing in Se vapor as a result of changes of the dominating defect type. For red crystals only big voids with lifetime of about 1021 ps are observed. Both methods suggest that greenish and red coloring of LiInSe2 are due to Se vacancies and interstitial Se atoms, respectively.

中文翻译：

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LiInSe2单晶结构缺陷的光学和正电子湮没研究

摘要 锂铟二硒（LiInSe2）是一种半导体材料，在非线性光学和中子探测方面具有广阔的应用前景。生长了具有不同（从绿色到红色）颜色的光学质量的 LiInSe2 晶体。基本吸收边的分析表明允许直接带间跃迁，并揭示导致价带和导带边缘模糊的结构无序。光致发光 (PL) 强度在化学计量组成的 LiInSe2 中较低，并且在样品在 Se 蒸气中退火后增加。408 nm 处的窄线与自由激子相关。PL 和 PL 激发光谱的分析允许人们将宽发射带与点缺陷以及自陷激子联系起来。由于主要缺陷类型的变化，在硒蒸气中退火后，平均正电子寿命增加。对于红色晶体，仅观察到寿命约为 1021 ps 的大空隙。这两种方法都表明 LiInSe2 呈绿色和红色分别是由于 Se 空位和间隙 Se 原子造成的。