Development of semiconductor compound materials & devices for radiation detection applications

Abstract

This thesis includes some efforts and results, reached at IMEM-CNR during the last three years, on both materials and devices for radiation detection applications. The first part of the thesis treats some basic concept of radiation detection. In particular the radiation concept, interactions radiation-matter and some medical applications of radiation are introduced. The physics of semiconductor radiation detectors is presented. The second part of the thesis treats the research on a new material: PbO. In particular presents the growth of polycrystalline and single crystal samples of \beta -PbO performed at IMEM-CNR using vapour approach. The samples were characterized with several techniques including: Photoluminescence, I-V characteristic, X-ray diffraction, TEM diffraction and Spectral Photoconductivity. In this thesis a diagnostic technique based on X-ray induce current developed at IMEM-CNR by the author of this thesis. By means of the described technique it was possible to measure the transport properties on PbO and CZT samples. In the third part of the work the research on CZT detectors is presented. The first part the preparation and characterization of CZT detector fabricated using the material grown at IMEM-CNR institute is presented. This part describes all the detector fabrication processes carried out at IMEM by undersigned, these processes include: Cutting, polishing, contact deposition and passivation. The undersigned was also involved in some parts of the growth of CZT ingots. The quality of CZT detectors can be evaluated by means of some characterizations including: I-V characteristic, resistivity measurement, transport properties measurement and spectroscopic performance. These characterizations are important in order to evaluate the quality of CZT material and the quality of the detector preparation process. In this thesis are presented also the results reached in the preparation and characterization of four CZT detectors developed in range of “3D CZT High Resolution Detectors” project leaded by Doc. Carl Budtz-Jorgensen and Doc. Irfan Kuvvetli, from National Space Institute of Technical University of Denmark (DTU Space Center). The aim of this project was to demonstrate that the good energy resolution of a new CZT drift strips detector can be combined with 3D sensing capabilities, very important features for X and gamma ray detectors for high energy astrophysics missions. IMEM institute was involved in some important parts of the project such as detector preparation, detector characterization and data analysis. This part presents all the steps of detector fabrication process and all the developments that were done in all single step of detectors preparation. For this project a new passivation process was developed at IMEM by the undersigned in collaboration with F. Pattini. In the final part of the thesis the detector characterization performed at European Synchrotron Radiation Facility (ESRF) in Grenoble is presented. All the detector preparation processes were carried out in IMEM by the author of this thesis in collaboration with Nicola Zambelli.