This work reports the effect of thermal annealing (350 °C and 450 °C) on structural, linear and non-linear optical properties of thermally evaporated Bi₇In₂₈Se₆₅ chalcogenide films of ∼800 nm thickness. The surface structure and elemental concentration were analyzed by the Field emission scanning electron microscope (FESEM) and Energy dispersive X-ray analysis (EDX). Based on the structural analysis, the 450 °C annealed film showed complete crystallinity whereas 350 °C annealed film showed less crystalline nature without much structural alterations from the as-prepared film which is mostly rhombohedral in nature. The Raman study showed the alteration on bonding in 450 °C annealed film than the as-prepared and 350 °C annealed films. The optical analysis by UV–Vis spectroscopy showed the decrease in transmittance and an increase in absorbance property with annealing. The direct bandgap and Tauc parameter decreased with annealing. Correspondingly, the refractive index increased along with other optical parameters such as lattice dielectric constant (ε_L), optical density (OD), skin depth (δ), real and imaginary dielectric constant (ε_r and ε_i), loss factor, volume energy loss function (VELF) and surface energy loss function (SELF) with annealing temperatures. The static linear refractive index (n₀) for the studied films showed an incremental behavior with annealing and satisfied Moss's rule. Such annealing induced higher absorption coefficient (α) and bandgap (E_g) along with other optical constants of the annealed films showed the possibility to be useful for solar cell, opto-electronic and nonlinear device applications.

这项工作报告了热退火（350 °C 和 450 °C）对热蒸发 Bi ₇ In ₂₈ Se _{65 的}结构、线性和非线性光学特性的影响约 800 nm 厚的硫属化物薄膜。通过场发射扫描电子显微镜（FESEM）和能量色散X射线分析（EDX）分析表面结构和元素浓度。根据结构分析，450°C 退火薄膜显示出完全的结晶度，而 350°C 退火薄膜显示出较少的结晶性质，与所制备的薄膜相比，其结构变化不大，主要是菱面体。拉曼研究表明，在 450 °C 退火膜中的键合比在制备时和 350 °C 退火膜中发生了变化。紫外-可见光谱的光学分析表明，随着退火，透射率降低，吸光度增加。直接带隙和 Tauc 参数随着退火而降低。相应地，_L )、光密度 (OD)、趋肤深度 (δ)、实部和虚部介电常数（ε _r和 ε _i）、损耗因子、体积能量损失函数 (VELF) 和表面能损失函数 (SELF) 与退火温度。所研究薄膜的静态线性折射率 (n ₀ ) 显示出随着退火和满足 Moss 规则而增加的行为。这种退火导​​致更高的吸收系数 (α) 和带隙 (E _g ) 以及退火薄膜的其他光学常数，显示出可用于太阳能电池、光电和非线性器件应用的可能性。