The ultraviolet absorption edge of stannic oxide (SnO2)
The ultraviolet absorption edge of stannic oxide (SnO2)
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DOI：
10.1016/0022-3697(64)90063-0
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发表时间：
1964-12
影响因子：
4
通讯作者：
R. Summitt;J. Marley;N. Borrelli
中科院分区：
文献类型：
--
作者：
R. Summitt;J. Marley;N. Borrelli
在300° K下获得了纯SnO 2单晶的紫外吸收边谱，吸收系数高达103 cm-1。偏振光的使用揭示了一个大的二向色性，吸收边不同ca0.3 eV的辐射偏振平行和垂直于晶轴。结果表明，这两个边缘代表本征跃迁，产生的直接能隙估计为3.93和3.57 eV的辐射极化平行（θ）和垂直（θ）的轴，分别。声子耦合跃迁的临界值约为3.7和3.4 eV，但间接跃迁似乎涉及几个晶格振动频率。在低吸收的两个边缘的形状差异产生的光偏振方向相反的轴的禁戒跃迁。为了解释这些观察结果，假设氧2能级在D4 h晶格中分裂成两个价带A2 u和Eusymmetry，其上边缘相差约0.3 eV。从这些价带到A1 g导带的电偶极跃迁的选择规则显示出不同的辐射极化方向。
The ultraviolet absorption edge spectrum of pure single crystal SnO2has been obtained at 300° K to absorption coefficients as high as 103cm−1. The use of polarized light revealed a large dichroism, the absorption edges differing byca0.3 eV for radiation polarized parallel and perpendicular to the crystal axis. The results suggest that both edges represent intrinsic transitions, and yield estimates for the direct energy gaps 3.93 and 3.57 eV for radiation polarized parallel (∥) and perpendicular (⊥) to thecaxis, respectively. Thresholds for phonon coupled transitions occur approximately 3.7 and 3.4 eV, but indirect transitions appear to involve several lattice vibrational frequencies. Shape differences in the two edges at low absorption arise from forbidden transitions for light polarized ∥ to thecaxis. To account for these observations, the oxygen 2plevels are assumed to split in theD4hcrystal lattice into two valence bands ofA2uandEusymmetry, with the upper edges differing byca0.3 eV. Selection rules for electric dipole transitions from these valence bands to theA1gconduction band are shown to be different for radiation polarized ∥ and ⊥ to thecaxis.