Recent Results in TlBr Detector Crystals Performance

Abstract

Recent developments in TlBr material preparation and growth technology have led to much improved crystal quality, detector performances and most importantly, reproducibility. In this paper, we describe some of the technological steps we have developed that have allowed us to produce reproducible spectrometric grade crystals for detector applications and present spectroscopic results. Typical crystals have a specific resistance of (3 5) 10 11 Ohm-cm and mobility-life time products of about 10 4 cm 2 /V, for both electrons and the holes. After fabrication into simple planar detectors of area 5 5 mm 2 and thickness 2 mm, spectral resolutions of 0. 8, 1.4, 2.1, and 7.1 keV, have been achieved at incident energies of 5.9, 59.6, 122, and 662 keV, respectively. These results were obtained without collimation or employing single carrier sensing or depth correction techniques.

Enhanced Born charge and proximity to ferroelectricity in thallium halides

“…2 TlBr has been investigated for radiation detection for several decades. [3][4][5] Some very encouraging results have been obtained, [6][7][8][9][10][11][12] showing that TlBr is a promising material for room-temperature spectroscopic gamma-ray detection. TlBr has high atomic numbers ͑Tl: 81 and Br: 35͒ and high density ͑7.56 g / cm 3 ͒, which lead to efficient radiation absorption.…”

Enhanced Born charges in III-VII,IV-VII2, andV-VII3compounds

“…7, 10, and 34͒ are generally smaller than that of TlBr. [35][36][37][38][39] This points to the need for further defect studies in these materials in order to better understand the transport properties and the performance of these materials as radiation detectors. The products of these materials may improve substantially in the future through better defect and impurity management.…”

Ionic current and polarization effect in TlBr

“…Using both the experimental and our theoretical data, we estimated the time required for the faster species, Br − ions, to traverse a distance of 1 mm in the crystal under 1000 V/cm bias at room temperature. We showed that this migration takes too long to account for the observed degradation of TlBr detectors in less than about 1 …”

“…1,2 The high performance stems from the material's favorable properties, namely, a moderate band gap (2.7 eV), very long carrier drift length (lifetime up to 10 −4 s) , high room-temperature resistivity (around 10 11 Ω.cm −1 ) 3 and high average atomic number. 4 However, its widespread adoption for radiation detection applications-such as medical and space imaging or port monitoring for national securityhas been prevented due to invariable performance degradation after operation times that vary from hours to several weeks.…”