Thallium lead iodide radiation detectors

Thallium lead iodide (TlPbI/sub 3/) is a compound semiconductor characterized with wide bandgap (2.3 eV) and high photon stopping power. 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/ powder with nominal purity of 99.99%. Powder X-ray diffraction analysis was performed to study 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 TlPbI/sub 3/ detectors exhibited resistivities higher 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 (122 keV) from a /sup 57/Co source. The TlPbI/sub 3/ detectors exhibited a clear peak of 5.48 MeV /spl alpha/-particles. Although the 122 keV peak was not resolved in the energy spectra, increased counts above the noise spectrum were observed by the present detectors.