Fabrication of indium iodide X- and gamma-ray detectors

Indium iodide (InI) is a compound semiconductor with a wide band gap. Due to its high atomic number (Z(In) : 49 and Z(I), : 53) and high density (5.31 g/cm(3)), InI exhibits high photon stopping power similar to that of CdTe. Since InI has wide band gap energy (2.0 eV), radiation detectors fabricated from InI are expected to realize low-noise operation at and above room temperatures. These physical properties indicate that InI is a very promising material for fabrication of room temperature X- and gamma-ray detectors. In this study, radiation detectors were fabricated from InI crystals. InI materials were purified by the multi-pass zone-refining method up to 80 times. InI crystals were grown by the traveling molten zone (TMZ) method with the zone-purified materials. The resultant InI radiation detectors were evaluated by measuring their electrical property, spectral responses and long-term stability. The resistivity of the InI detectors were found to be approximately 3 x 10(9) (Omega cm). The InI detector exhibited a clear peak corresponding to 22 keV X-rays from a Cd-109 radioactive source at room temperature. To evaluate the long-term stability of the InI detectors, temporal change of the energy spectra of the detectors was measured for a period of time at 20 degrees C and at -20 degrees C. At 20 degrees C, the InI detectors exhibited some degradation in spectral response. On the other hand, the InI detectors operated stably for more than 32 hours at -20 degrees C.