Charge Sharing on Monolithic CdZnTe Gamma-Ray Detectors: A Simulation Study

International audienceMonolithic CdZnTe gamma-ray detectors are used to build gamma cameras for nuclear medicine imaging but their energy resolution is currently limited by charge sharing between adjacent anodes. For this work, charge sharing is simulated using Ulysse, a numerical model that takes into account the physical processes of charge creation by ionizing radiation and charge transport within the semiconductor detector. The charge carrier cloud size, following the gamma-ray photon interaction, is computed by the Monte Carlo method. Electron cloud diffusion and charge induction on the electrodes are computed by the finite element method. This study shows that the electron diffusion strongly influences the final electron cloud diameter

Optimization of the Growth Conditions for High Quality CH 3 NH 3 PbBr 3 Hybrid Perovskite Single Crystals

International audienceOrganic-Inorganic Halide Perovskite, hybrid perovskite, CH3NH3PbBr3, MAPbBr3, Crystal Growth, Crystalline quality, structural defects ABSTRACT Methylammonium lead tribromide (CH3NH3PbBr3) single crystals has gained a growing attention in the past few years due to their use as model material to investigate relevant intrinsic perovskite properties, and for their potential applications for radiation detection. Their study has been facilitated by the ease and speed of fabrication of millimetric single crystals through a simple protocol of unseeded Inverse Temperature Crystallization (ITC). In this study, we show that such growing conditions suffer from both insufficient reproducibility regarding crystal quality and low yield of single crystal obtention. In particular, we observed that more than the half of crystals obtained by this technique are polycrystals. The structural defects of the rest single crystals obtained have been characterized by cross polarized light, surface chemical etching to reveal dislocations, X-ray diffraction, ICP-MS, and H-NMR. The results reveal a strong variability of crystals regarding to internal strains and dislocation densities. Such defects can further severely impact the electronic transport properties of these materials. A more robust and reproducible protocol is proposed based on seeded growth combined with appropriate temperature profile selected from continuous crystal growth monitoring. A clear improvement in crystal quality is reached with higher transparency, minimized internal strains and a low dislocations density in the range of 104 to 105 cm-2

On the influence of dislocation walls in CdTe:Cl

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