Thallium lead iodide radiation detectors

Abstract

Thallium lead iodide (TlPbI/sub 3/) is a compound semiconductor characterized with wide band gap (2.3 eV) and high photon stopping power. Thus, TlPbI/sub 3/ is an attractive material for fabrication of room temperature radiation detectors. In this study, TlPbI/sub 3/ crystals were grown by the vertical Bridgman technique using zone-purified materials. The starting materials for the crystal growth were synthesized from commercially available TlI and PbI/sub 2/ powders with nominal purity of 99.99%. Powder X-ray diffraction analysis was performed to evaluate chemical composition of the synthesized TlPbI/sub 3/. In order to fabricate radiation detectors, the grown crystals were cut into several wafers using a wire saw. The wafers were then polished using Al/sub 2/O/sub 3/ abrasives. Electrodes were formed on the wafers by vacuum evaporation of gold. The resultant TlPbI/sub 3/ radiation detectors were evaluated by measuring their current-voltage characteristics and spectral responses. Most of TlPbI/sub 3/ detectors exhibited resistivities more than 10/sup 11/ /spl Omega/cm. The TlPbI/sub 3/ detectors were irradiated with /spl alpha/-particles (5.48 MeV) from a /sup 241/Am source or /spl gamma/-rays (662 keV) from a /sup 137/Cs source. The TlPbI/sub 3/ detectors exhibited a clear peak of 5.48 MeV /spl alpha/-particles. Although the 662 keV peak was not resolved in the energy spectra, increased counts above the noise spectrum were observed for the detectors. To our knowledge, it is the first time that TlPbI/sub 3/ detectors exhibit /spl alpha/-particle spectra with a clear peak and /spl gamma/-ray spectra.