## Author
Song Zhang (a), Hui Zhang (b)
(a) Institute for Aero Engine, Tsinghua University, Beijing, China
(b) School of Safety Science, Tsinghua University, Beijing, China
## Abstract
CdZnTe crystals with large single-crystal volume have been grown using the travelling heater method. The concentration uniformity, structural defects, and resistivity of the THM crystals were measured. Two planar detectors were fabricated, which achieved a best resolution of 5.12 % at 59.5 keV and a μeτe value of 8.0 × 10−3 cm2/V. A quasi-hemispherical detector was further prepared and achieved a resolution of 2.27 % at 662 keV and a Peak-to-Compton Ratio of 4.76. Progress in crystal growth, processing, detector fabrication and characterization methods and tools contributed to improvement of high-quality CdZnTe crystals for nuclear radiation detectors.
## Introduction
CdZnTe crystals have attracted wide attention due to their unique advantages in nuclear radiation detection and medical imaging [[1], [2], [3], [4]]. For CdZnTe crystals, traveling heater method (THM)-grown crystals account for most commercial high-quality products [[5], [6], [7], [8]]. The traveling heater method has been proven to have excellent longitudinal homogeneity of as-grown crystals, low growth temperature, and low defect density. Unlike the Vertical Bridgman method or other similar melt growth methods, the dissolution of feed and the growth of single crystal are carried out simultaneously during THM growth, which requires better control of the melt flow, and the coordination between thermal field and solution zone.
By connecting the measurable parameters with simulation results of self-programmed “MASTRAPP” software, the authors studied the multi-scale physics processes in THM, involving complex interactions of fluid flow, mass and heat transfer, dissolution and solidification, and their couplings. Several important conclusions were obtained regarding understanding of wall nucleation [9], shape and stability of growth interface [10], rotation control of ACRT [11], and thermal field design of the THM growth furnace [12]. Based on the knowledge above, CdZnTe crystals from 1 in. to 3 in. with quite large crystal grains have been successfully grown. However, a great deal of information, such as concentration uniformity [5,13], purity of as-grown crystals [14], structural defects and electrical properties [15], are needed to understand the quality of as-grown crystals when making detectors. Also, the energy resolution and mobility life product of electrons are also important parameters for applications in nuclear radiation detection, which always use a single-polarity charge collection structure [16].
In this study, the latest crystal growth results of CdZnTe are presented. The characterization methods and results of the CdZnTe crystal material are discussed. Finally, several detectors made with in-house grown CdZnTe crystals, aiming at applications in nuclear radiation detection, are tested.
CdZnTe Association (CdZnTe.com)
https://www.cdznte.com/thesis/characterization-of-thm-cdznte-for-nuclear-radiation-detection.html