Bismuth chalcohalide-based nanocomposite for application in ionising radiation detectors

Abstract

Bismuth sulpho iodide (BiSI) belongs to the family of chalcohalides, which present several attractive electro-optic properties. In particular, BiSI is a semiconductor which could be used in X and gamma ray detection due to a band gap of 1.6 eV, density of 6.4 g cm−3, and absorption coefficient for 60 keV radiation of 5.6 cm2 g−1. This work presents a facile synthesis under solvothermal conditions of a nanocomposite consisting of BiSI nanorods and amorphous carbon structures. Furthermore, it studies its ionising radiation detection properties at room temperature, when prototype detectors were built from pellets. The construction conditions of pellets were also studied, varying the applied pressure and heat treatment to the nanocomposite. Dark current density and response to different exposure rates of a 241Am source were measured for the prototype detectors built. It was found that heat treatment of pellets considerably improves detectors performance. Dark current density was one order of magnitude lower than for the pellets without heat treatment, and its response to the 241Am source, linear, with a signal to noise ratio of 7 for 20 V. Finally, the resistivity for the heat treated detector was in the order of 1011 Ω cm, comparable to other materials studied for this application.