High Efficiency, Room Temperature Semiconductor Detectors

Prevention of the spread of nuclear weapons has reached a state of heightened urgency since the events on September 11, 2001. Gamma ray spectrometers are important tools in homeland security to check the spread of nuclear materials and weapons. Important requirements for gamma ray spectrometers used in this application include good energy resolution, high detection efficiency, compact size, light weight, easy portability and low power consumption. None of the currently available detectors meet all of these requirements. In the proposed effort, we plan to explore a wide bandgap semiconductor material, thallium bromide (TlBr), as a room temperature detector for nuclear monitoring. TlBr has high density (7.5 g/cm3) and atomic number constituents for high gamma ray stopping power, and high resistivity (>1010 Wcm) for low noise device operation. Furthermore, the material melts congruently at a modest temperature (480 ¿ C), which allows use of melt-based crystal growth approaches to produce large volume crystals. Recent results indicate that through sufficient material purification, charge transport properties approaching those of CZT can be achieved. The goal of the proposed project is to perform rigorous investigation of purification and crystal growth of this promising material to produce high performance TlBr gamma-ray spectrometers for homeland security.