Semiconductor Detectors Fabricated from TlBr Crystals
- PDF / 546,533 Bytes
- 7 Pages / 432 x 648 pts Page_size
- 84 Downloads / 182 Views
Semiconductor Detectors Fabricated from TlBr Crystals Keitaro Hitomi1, Tsutomu Tada1, Seong-Yun Kim1, Yan Wu1, Hiromichi Yamazaki1, Tadayoshi Shoji2 and Keizo Ishii3 1 Cyclotron and Radioisotope Center, Tohoku University, Sendai 980-8578, Japan 2 Department of Electronics and Intelligent Systems, Tohoku Institute of Technology, Sendai 982-8577, Japan 3 Department of Quantum Science and Energy Engineering, Graduate School of Engineering, Tohoku University, Sendai 980-8579, Japan ABSTRACT Frisch collar detectors were fabricated from TlBr crystals with the dimensions of 2 mm × 2 mm × 4.4 mm. Spectroscopic performance of the TlBr Frisch collar detectors was evaluated at room temperature. An energy resolution of 2.9% FWHM at 662 keV was obtained from the detector without the depth correction. The detector exhibited stable spectral performance for 12 hours. Direct measurements of electron mobility-lifetime products were performed with the detectors. The TlBr crystals exhibited the electron mobility-lifetime products of ~10-3 cm2/V at room temperature. INTRODUCTION Thallium bromide (TlBr) is a compound semiconductor promising for fabrication of efficient radiation detectors with high energy resolutions at room temperature. The TlBr crystals exhibit high photon stopping power originating from its high atomic numbers (Tl: 81, Br: 35) and high density (7.56 g/cm3). The wide bandgap energy (2.68 eV) results in the high resistivity of TlBr crystals (~1010 Ω·cm) at room temperature [1], enabling the device to operate with low noise. The charge transport properties in TlBr crystals were improved significantly by purification of the starting material [2]. The mobility-lifetime products for electrons and holes in TlBr crystals were reported to be ~10-3 cm2/V and ~10-4 cm2/V, respectively [2]. The TlBr melts congruently at the melting point of 460 °C and has no destructive phase transition between the solidification and room temperature. The purification and crystal growth of TlBr can be performed simply from the melt. Due to its attractive physical properties, semiconductor detectors fabricated from TlBr crystals were studied by numerous researchers [1-8]. The thickness of TlBr detectors with planar electrodes was limited to less than 1 mm due to the hole trapping effects. Pixelated TlBr detectors were fabricated for overcoming the problem by the small pixel effect [9] and demonstrated improved energy resolutions [8,10]. In order to solve the hole trapping problem, the Frisch collar detectors were fabricated from TlBr crystals in this study. The Frisch collar detector operates as a single polarity charge sensing device, in which the induced charge on the anode depends mainly on the collection of electrons and scarcely affected by the hole movement. The Frisch collar detector design was applied to CdZnTe, HgI2 and TlBr, and the detectors exhibited excellent spectroscopic performance [11-15].
111
In this study, spectroscopic performance of TlBr Frisch collar detectors was evaluated at room temperature. Direct measurements of elect
Data Loading...
