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Thallium bromide (TlBr) has been under development for room temperature gamma ray spectroscopy. As a result of improvements in material processing and detector fabrication over the last several years, the electron and hole mobility-lifetime products of TlBr are close to those of CdTe. This has allowed us to fabricate 10 mm thick arrays. Without any correction, 4.1% FWHM energy resolution was measured from one pixel of 3x3 array at 662 keV at room temperature. To minimize the polarization effect, lowering the operation temperature was applied to 13 mm thick array and the stable operation beyond 8 months could be seen without any significant degradation of detector performance. Much improved energy resolution of 2.2% or less at 662 keV has been also obtained from one pixel with depth correction. In this paper improved charge collection with Cr contacts and our recent progress made in long term stability of TlBr detectors at room temperature by applying post annealing are presented. [ABSTRACT FROM PUBLISHER]

Abstract: TlBr and TlBr x I1− x are wide bandgap semiconductor materials being investigated for applications in γ-ray spectroscopy. They have a good combination of density and atomic numbers, promising to make them very efficient detectors. Their low melting points and simple cubic and orthorhombic crystal structures are favorable for bulk crystal growth. However, these semiconductors need to be extremely pure to become useful as radiation detectors. Impurities can lead to charge trapping and scattering, reducing the charge transit lengths and limiting the detector thickness to <1mm. Additional purification steps were implemented to improve the purity and mobility–lifetime product (μτ) of electrons. Detector-grade TlBr with the electron μτ product of up to 6×10−3 cm2/V has been produced, which allowed operation of detectors up to 15mm thickness. The ternary TlBr x I1− x was investigated at different compositions to vary the bandgap and explore the effect of added TlI on the long term stability of detectors. The material analysis and detector characterization results are included. [Copyright &y& Elsevier]