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Thallium bromide (TlBr) is a compound semiconductor with a band gap of 2.68 eV making it ideal for room temperature radiation detection. The high atomic numbers, 81 and 35, and the high density of 7.56 g/cm 3 give it excellent gamma-ray stopping power. TlBr is a cubic material that melts congruently at a relatively low temperature (∼480 • C). These properties make it relatively easy to grow good quality crystals with high yield. As a result of improvements in the purification of TlBr mobility-lifetime product of electrons, µτ e , is now on the order of 10 −2 cm 2 /V, which is similar to that of CZT. High µτ e enables the fabrication of thicker detectors with good charge collection and energy resolution. The properties of TlBr make it ideal for use in room temperature gamma radiation operation [1]. Single carrier devices such as small pixel arrays [2] and Frisch collar devices [3] which were developed for CZT can also been applied to TlBr. For example, better than 1% FWHM at 662 keV has been obtained for single pixel events with small (e.g., 3 × 3 pixels, 1-mm pitch, 5-mm thick) arrays.

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In this paper, the electronic properties of CdTe (100) films without impurities and with the addition of O2 molecules were investigated based on calculations from first principles. It was found that when the oxygen concentration increases from 8 to 14 %, the O2 molecule passes the energy barrier more easily, which indicates an increase in the catalytic activity of the CdTe film. Since oxygen affects the catalytic process, we recorded the movement of the band gap depending on the oxygen concentration. According to the calculated results of the study of small diatomic and triatomic clusters (Te, Cd), we found that the inclusion of oxygen atoms or atoms of other kinds in small clusters (Te, Cd) affects the catalytic activity of the studied systems as a whole.

Thallium bromide (TlBr) is a promising material for room temperature gamma radiation detection due to its high density, high atomic number, and wide bandgap. Additionally, TlBr has a cubic crystal structure and melts congruently at a relatively low temperature. Advances in material purification, crystal growth and device processing have led to improved material quality including a significant increase in the mobility-lifetime product of electrons in TlBr. This has enabled single carrier collection devices with thicknesses of 1 cm and beyond. The arrays have been flip-chip bonded to carrier boards using a low temperature curing conductive polymer. In this paper we report on results from planar and pixelated devices. Planar TlBr devices with dimensions of 12 mm × 12 mm × 7 mm exhibit an energy resolution ranging from 3% to 5% FWHM at 662 keV when using a shaping time of 2 s. The energy resolution in planar devices improves with a reduction of the shaping timing consistent with the expected amelioration of the depth dependence. The 1-cm thick pixelated arrays, with a pitch of 1.72 mm, produce an energy resolution in the anode spectrum ranging from 1.8% to 4.4%, without applying depth corrections. This work presents spectra from a selected pixel for 133Ba and 57Co irradiation. Measurements of the room-temperature stability of the planar and pixelated detectors show that the position of the 662-keV photopeak is stable over a period of ~200 days, but the shape of the photopeak in the anode spectra exhibits small changes. These detectors show promise for applications in radio-isotope identification devices and for medical imaging.