Surface and bulk defects in cadmium zinc telluride and cadmium manganese telluride crystals

Abstract

This dissertation reports the study of defects in Cadmium Zinc Telluride (CZT) and Cadmium Manganese Telluride (CMT) nuclear detectors. In this dissertation I studied the defects associated with surface processing of detectors as well as the extended defects present in the crystals. Synchrotron radiation, Infrared microscopy and Atomic Force Microscopy were employed to identify and study the defects. Detector response and performance from x-ray mapping and external sources was correlated with the observed defects. The Pockels electro-optic effect was used to observe non-uniformities of the internal electric field caused by defects. This collection of data was employed to produce a counting algorithm to show the expected performance of detectors based on sizes, concentration and distribution of inclusions. An optimal surface processing method combining polishing and chemical etching was established. Finally the first response of a CMT detector to high energy gamma radiation was demonstrated.