Zone refining and crystal growth of Bismuth tri-iodide crystals

Bismuth tri-iodide is a promising candidate for room temperature radiation detection because of its wide band gap energy. This material has higher effective atomic number as compared to germanium and CdZnTe. Its higher density results in improved stopping power for photons. But the presence of impurities limits the expected properties up to a large extent. Reduction of impurity concentration can lead to significant improvement in the properties like resistivity, charge transport and spectroscopic performance of detectors. In this study, zone refining technique has been employed to get detector grade refined material. ICP-MS technique was used to analyze the impurity concentration before and after zone refining. Bismuth tri-iodide single crystals were grown using Bridgman technique. Electrical contacts of Initial detectors are made using gold and silver paste. Detectors were tested by measuring their leakage current and resistivity.