Abstract Bi2Se3 bulk alloys were synthesized using a standard mono-temperature melting process and used as source materials to deposit thin films on non-conductive super cleaned glass substrates by a vacuum thermal evaporation technique. Both bulk and thin-film samples were polycrystalline as confirmed by X-ray diffraction patterns. The film samples were subjected to the annealing process in air atmosphere at 250 and 300 ℃ for 3 h, aiming to boost the optical properties, in particular, to enhance the light transmission. The surface roughness, morphology and granular structure were investigated by atomic force microscope and scanning/transmission electron microscopes. The correlation between structural changes due to annealing and optical properties was observed. For a higher annealing temperature of 300 ℃ , the coefficient of transmittance increased reaching 80–90% in the IR range. Consequently, the absorption coefficient greatly decreased by annealing, especially for low photon energies. The optical band gap corresponds to the direct transition and increased notably by annealing from 1.51 to 1.83 eV. The spectra of optical parameters including the refraction index, coefficient of extinction and complex-valued dielectric function were deduced from the transmittance/reflection measurements to evaluate the effect of annealing. The energy loss functions were also estimated demonstrating that the volume and surface energy losses are of the same order.

中文翻译：

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制备和退火的 Bi2Se3 薄膜的结构和光学特性的相关性

摘要 使用标准的单温熔化工艺合成了 Bi2Se3 块状合金，并将其用作原材料，通过真空热蒸发技术在非导电超清洁玻璃基板上沉积薄膜。X 射线衍射图证实，块状和薄膜样品都是多晶的。薄膜样品在空气气氛中在 250 和 300 ℃ 下进行 3 小时的退火过程，旨在提高光学性能，特别是提高透光率。通过原子力显微镜和扫描/透射电子显微镜研究表面粗糙度、形貌和颗粒结构。观察到由于退火引起的结构变化与光学特性之间的相关性。对于300℃的更高退火温度，在红外范围内，透射系数增加到 80-90%。因此，通过退火，吸收系数大大降低，特别是对于低光子能量。光学带隙对应于直接跃迁，并通过从 1.51 eV 退火到 1.83 eV 显着增加。从透射/反射测量中推导出包括折射率、消光系数和复值介电函数在内的光学参数的光谱，以评估退火的效果。还估计了能量损失函数，证明体积和表面能损失具有相同的数量级。光学带隙对应于直接跃迁，并通过从 1.51 eV 退火到 1.83 eV 显着增加。从透射/反射测量中推导出包括折射率、消光系数和复值介电函数在内的光学参数的光谱，以评估退火的效果。还估计了能量损失函数，证明体积和表面能损失具有相同的数量级。光学带隙对应于直接跃迁，并通过从 1.51 eV 退火到 1.83 eV 显着增加。从透射/反射测量中推导出包括折射率、消光系数和复值介电函数在内的光学参数的光谱，以评估退火的效果。还估计了能量损失函数，证明体积和表面能损失具有相同的数量级。