Garg Alka, Jindal Ruby
Gargi College, University of Delhi, New Delhi, 110049, India.
School of Basic and Applied Sciences, K.R. Mangalam University, Gurugram, Haryana, 122103, India.
Appl Radiat Isot. 2025 Feb;216:111598. doi: 10.1016/j.apradiso.2024.111598. Epub 2024 Nov 24.
Thin films of Bismuth Tri-iodide BiI were synthesized on a glass substrate by the thermal vacuum deposition technique. Films were exposed to gamma radiations of two doses 10 Gy and 50 Gy. Structural and optical properties of films were studied through X-ray Diffraction and UV spectroscopy both before and after the gamma irradiation. The effect of gamma radiations on microstructure parameters i.e. crystallite size and the micro-strain were studied qualitatively and quantitively. The observed increase in crystallite size and decrease in micro-strain is due to localized heating of crystallites which results in the merging of small crystallites and their assembly leading to the formation of larger crystallites as evident from X-ray Diffraction after gamma irradiation. Effect on the optical constants namely refractive index and extinction coefficient for different doses was also enumerated to throw light on the change in optical density of this material on gamma irradiation. It is observed that the refractive index n increases with an increase in the doses of gamma irradiation. The increase in optical density could be attributed either to the displacement of atoms from lattice sites to the interstitial sites or to the self-assembly behavior of the crystallites on irradiation. The absorption coefficient follows Urbach's empirical relation and exhibits exponential dependency on photon energy close to the band edge. Calculating Urbach's energy provides insight into the emergence of localized states at the energy gap's edges.
通过热真空沉积技术在玻璃基板上合成了三碘化铋（BiI₃）薄膜。将薄膜暴露于10 Gy和50 Gy两种剂量的伽马辐射下。在伽马辐照前后，通过X射线衍射和紫外光谱对薄膜的结构和光学性质进行了研究。定性和定量地研究了伽马辐射对微晶尺寸和微应变等微观结构参数的影响。观察到微晶尺寸增加和微应变减小是由于微晶的局部加热，这导致小微晶合并并组装形成更大的微晶，伽马辐照后的X射线衍射结果证明了这一点。还列举了不同剂量对光学常数（即折射率和消光系数）的影响，以阐明该材料在伽马辐照下光密度的变化。观察到折射率n随着伽马辐照剂量的增加而增加。光密度的增加可能归因于原子从晶格位置位移到间隙位置，或者归因于辐照时微晶的自组装行为。吸收系数遵循乌尔巴赫经验关系，并且在接近带边处对光子能量呈现指数依赖性。计算乌尔巴赫能量有助于深入了解能隙边缘处局域态的出现。
