%0 Journal Article
%T Synthesis and Characterisation of Thin Films of Bismuth Triiodide for Semiconductor Radiation Detectors
%A Alka Garg
%A Monika Tomar
%A Vinay Gupta
%J Conference Papers in Science
%D 2014
%R 10.1155/2014/370436
%X Bismuth iodide is a potentially active material for room temperature radiation detector, as it is well reported in the literature that it has both wide energy band gap and high atomic absorption coefficient. Crystalline films of high atomic number and high radiation absorption coefficient can absorb the X-rays and convert them directly into electrical charges which can be read by imaging devices. Therefore, it was proposed to grow thin films of Bismuth iodide on glass substrate using thermal evaporation technique in vacuum to avoid the inclusion of impurities in the films. The structural studies of the films were carried out using XRD and optical absorption measurement was carried out in the UV/VIS region using spectrophotometer. All Bismuth iodide films grown at room temperature are polycrystalline and show X-ray diffraction peaks at angles reported in research papers. The optical transmission spectra of BiI3 films show a high transmission of about 80% in visible region with a sharp fall near the fundamental absorption at 650£¿nm. Resistivity of the as-grown film was found to be around 1012£¿ohm-cm suitable value for X-ray detection application. Films were subjected to scanning electron microscopy to study the growth features of both as-grown and annealed films. 1. Introduction Gamma ray detectors have become increasingly important for the application of medical imaging and environmental safety. Photographic films, Phosphor screens, and Silicon array have been used as imaging detectors for many years but all these devices are indirect detectors with low efficiency and poor spatial resolution. Compound semiconductors are the most promising radiation detector compared to high purity Ge and Si because of their moderate band gap and ability to operate at room temperature [1]. Bismuth iodide is one such compound semiconductor with potential for room temperature gamma and X-ray detection applications [2]. Bismuth Triiodide is having both high atomic number and high absorption coefficient, important parameters for material to detect X-rays and Gamma rays [3]. Bismuth Triiodide is a layered compound having low melting point of 408¡ãC. BiI3 is stable within the range from melting point to room temperature [4]. BiI3 is reported to have vapor pressure of around 90£¿mbar at temperatures 250¡ãC to 300¡ãC [5, 6]. Therefore, BiI3 films can be grown from both liquid and vapour phases. BiI3 has been reported with different band gap characteristics and values. Experimentally and computationally, band gap value is ranging from 1.5£¿eV to 2.2£¿eV [7]. It is reported that BiI3 has
%U http://www.hindawi.com/journals/cpis/2014/370436/