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首页> 外文期刊>Journal of Applied Physics >Crystal growth, structural, and optical characterization of the ordered defect compound CuGa_(5)Se_(8)
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Crystal growth, structural, and optical characterization of the ordered defect compound CuGa_(5)Se_(8)

机译:有序缺陷化合物CuGa_(5)Se_(8)的晶体生长,结构和光学特性

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The crystal structural and optical properties of the ordered defect compound CuGa_(5)Se_(8) grown by the vertical Bridgman-Stockbarger method have been studied by x-ray diffraction and optical absorption techniques, respectively. The analysis of the x-ray diffraction data shows that the material crystallizes in a tetragonal chalcopyrite-related structure with unit cell parameters a=5.4732(8) and c=10.931(6) A. Optical data shows that the band gap energy E_(G) varies from 1.917 to 1.811 eV in the temperature range between 10 and 300 K. It is found that the variation of E_(G) with T is mainly due to the contribution of optical phonons with a characteristic phonon energy of about 19 meV. The optical absorption coefficient just below the absorption edge varies exponentially with photon energy confirming the existence of the expected Urbach's tail. The phonon energy hv_(p) associated with Urbach's tail, which is found to be 54 meV, is about two times higher than the highest optical phonon mode reported for ternary semiconductors of the Cu-Ga-Se system. The origin of higher energy is attributed to the contribution of localized modes produced by structural disorders of low energy formation mainly due to deviation from ideal stoichiometry.
机译:通过X射线衍射和光吸收技术分别研究了通过垂直Bridgman-Stockbarger方法生长的有序缺陷化合物CuGa_(5)Se_(8)的晶体结构和光学性质。 X射线衍射数据的分析表明,该材料以单位面积参数a = 5.4732(8)和c = 10.931(6)A的四方黄铜矿相关结构结晶。光学数据表明,带隙能E_( G)在10到300 K之间的温度范围内从1.917到1.811 eV不等。发现E_(G)随T的变化主要是由于具有特征声子能量约为19 meV的光学声子的贡献。吸收边缘正下方的光吸收系数随光子能量呈指数变化,从而确认了预期的Urbach尾巴的存在。与Urbach尾部相关的声子能量hv_(p)被发现为54 meV,比报道的Cu-Ga-Se系统三元半导体的最高光学声子模式高大约两倍。较高能量的起源归因于低能量形成的结构紊乱所产生的局部模式的贡献,这主要是由于偏离了理想的化学计量比。

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