The Influence of Thermal Treatment on Monocrystalline CZT and Tellurium Inclusions

Abstract

ABSTRACTCadmium Zinc Telluride (CZT), considered as a viable material for use in room temperature radiation detectors, has an undesired presence of tellurium inclusions in the bulk. Thermal treatment, in the form of annealing, has been utilized to test the viability of refining CZT into better detector material, either by the elimination of the tellurium inclusions or by the migration of the inclusions under a temperature gradient, but usually with a deterioration of electrical properties. We took infrared micrographs and current voltage (IV) characteristics of CZT samples prior to thermal treatment. We carried out 24-hour thermal treatments with a range of temperature from 100°C to 700°C to determine an optimal annealing temperature and to verify changes in the sizes, morphologies, and locations of the tellurium inclusions on the surfaces and within the crystal bulk of the CZT. The IV curves and resistivities prior to and after thermal treatments were compared, as were the infrared micrographs before and after annealing. Also, the changes in electrical properties of the samples with annealing conditions were compared against structural changes monitored at the same steps during the annealing process, in order to understand the effects of the thermal annealing to the radiation detector properties of the material. Correlations between the shape, size and position of inclusions and electrical properties of the material were attempted.