Formation and characterization of a CuPt-A type ordered structure in cadmium zinc telluride single crystals

Abstract

Cadmium zinc telluride (CdZnTe) single crystals have been widely utilized in various photoelectron devices such as radiation detectors and solar cells. Different types of ordered phases have also been investigated in CdZnTe thin films grown on various substrates, which have been confirmed to have great influence on the properties of materials and performance of devices. This work, for the first time, provides direct evidence of the existence of a CuPt-A type ordered structure in CdZnTe bulk single crystals. The structure and distribution of the ordered phases have been comprehensively investigated by transmission electron microscopy (TEM). The results indicated that such a CuPt-A type ordered structure with two variants exhibits the same structure feature as that previously reported in CdZnTe thin films. In contrast, no ordering phenomenon can be found in CdTe single crystals, which has proved that the ordering is caused by the introduction of Zn²⁺ ions. With the help of a series tilting experiment, the alternately arranged Cd²⁺ and Zn²⁺ ions at {111} planes along <111> direction have been confirmed to be the reason for the formation of such ordered phase. The local enrichment of Zn²⁺ has also been confirmed for the ordered phase, which is also the reason why it was only found at the Zn-rich head of the ingot. Based on the experimental results, the possible crystal structure and the formation mechanism of such ordered CdZnTe have also been proposed accordingly.