Thallium lead iodide radiation detectors

Thallium lead iodide (TlPbI₃) is a compound semiconductor characterized with wide bandgap (2.3 eV) and high photon stopping power. TlPbI₃ is an attractive material for fabrication of room temperature radiation detectors. In this study, TlPbI₃ 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 PbI₂ powder with nominal purity of 99.99%. Powder X-ray diffraction analysis was performed to study chemical composition of the synthesized TlPbI₃. In order to fabricate radiation detectors, the grown crystals were cut into several wafers using a wire saw. The wafers were then polished using Al₂O₃ abrasives. Electrodes were formed on the wafers by vacuum evaporation of gold. The resultant TlPbI ₃ radiation detectors were evaluated by measuring their current-voltage characteristics and spectral responses. Most TlPbI₃ detectors exhibited resistivities higher than 10¹¹ Ωcm. The TlPbI₃ detectors were irradiated with α-particles (5.48 MeV) from a ²⁴¹ Am source or γ-rays (122 keV) from a ⁵⁷Co source. The TlPbI₃ detectors exhibited a clear peak of 5.48 MeV α-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.