Quality assessment of Cadmium Telluride as a detector material for multispectral medical imaging

TL;DR

This paper evaluates the quality of Cadmium Telluride crystals for multispectral medical imaging detectors, focusing on defect analysis, surface properties, and prototype testing to improve detector performance.

Contribution

It introduces a comprehensive quality assessment method for CdTe crystals, including defect mapping and surface analysis, to enhance detector development for medical imaging.

Findings

Infrared microscopy reveals defect distributions in CdTe crystals.

IV measurements identify optimal surface for pixelization.

Prototype tests demonstrate potential for improved multispectral imaging.

Abstract

Cadmium Telluride (CdTe) is a high-Z material with excellent photon radiation absorption properties, making it a promising material to include in radiation detection technologies. However, the brittleness of CdTe crystals as well as their varying concentration of defects necessitate a thorough quality assessment before the complex detector processing procedure. We present our quality assessment of CdTe as a detector material for multispectral medical imaging, a research which is conducted as part of the Consortium Project Multispectral Photon-counting for Medical Imaging and Beam characterization (MPMIB). The aim of the project is to develop novel CdTe detectors and obtain spectrum-per-pixel information that make the distinction between different radiation types and tissues possible. To evaluate the defect density inside the crystals -- which can deteriorate the detector performance -- we employ infrared microscopy (IRM). Posterior data analysis allows us to visualise the defect distributions as 3D defect maps. Additionally, we investigate front and backside differences of the material with current-voltage (IV) measurements to determine the preferred surface for the pixelisation of the crystal, and perform test measurements with the prototypes to provide feedback for further processing. We present the different parts of our quality assessment chain and will close with first experimental results obtained with one of our prototype PC detectors in a small tomographic setup.