Weibin Zhu

Effects of sample processing on the performance of CdZnTe crystals

Due to the outstanding properties of CdZnTe materials, CdZnTe detectors have been the research focus for X- and gamma ray applications for many years. For CdZnTe detector fabrication heat treatments are often desirable. In order to provide detailed information of the CdZnTe crystal temperature tolerance during the detector fabrication procedure, and determine if performance degradations are from elevated temperatures or other processing steps, we tested the leakage current variation of raw CdZnTe crystals with temperature and during the crystal processing. The studies were conducted on (111)-oriented CdZnTe crystals provided by Yinnel Tech. Due to the 111 orientation, the CdZnTe crystals show a Cd rich side (A side) and a Te rich side (B side). These two sides revealed entirely different character variation. Preliminary experimental results are provided here

Multi-energy detection using CdZnTe semiconductor detectors

The CdZnTe semiconductor detectors have been widely applied in radiation detection, space physics, medical imaging systems and security inspection field. In order to improve the imaging quality and to provide material identification, dual energy and multi-energy detection technology are often necessary. Here we provide a CdZnTe multi-energy detection technology. Micro-strip anode are separated to several segments along the X ray incidence direction. These different segments of electrodes are used as different energy detection regions, from low energy regions to high energy regions. Under this contact geometry the multi-energy information could be obtained, at the same time the detection efficiency of CdZnTe detectors could be improved by the increase of the detector size, not the thickness. So the charge collection efficiency and the operation voltage would be kept invariable. This technology will also solve the problem that the low energy detector is too thin to fabricate for traditional dual energy solid detectors. The data correction in different energy regions could be performed according to the simulation results of the energy deposition distribution in CdZnTe detectors of different energy X rays. This paper provides the details of the multi-energy detection technology.

Signals from guard rings on side wall of CZT detectors

Researches on CZT detectors emphasize on how to correct the incomplete charge collection due to the defects in CZT crystals and to improve the performance of CZT detectors. Normally to reduce the surface leakage current and to shape the weighted electric field the guard ring on side wall or on the anode surface surrounding the pixel is applied. Because the guard ring is on the side wall of CZT detectors and is sensitive to the transfer of induced electrons and holes, we expected that the signals from the guard ring could provide the charge transfer information. At first we simulated the electric field inside planar CZT detectors and pixel CZT detectors with single guard ring covering the whole side walls or double guard rings (one is close to the pixel surface and another one is close to the cathode surface). We also changed the electrode surface size and kept the thickness unchanged to compare the variation of the inside field. Preliminary results are provided here

Effects of different orientation on CdZnTe detectors

The traditional orientation used for CdZnTe detectors is (111) surface. To improve the single crystal yield and effectively utilize one oven crystal ingot, we tested CdZnTe detector speciality whose (115) orientation was taken as contact surfaces. Through the same processing as that of (111) orientation we made three pixel CdZnTe detectors. Their performance were tested and compared with that of (111) orientation CdZnTe detectors. The preliminary results were provided here.