Searching for better X-ray and γ-ray photodetectors: structure-composition properties of the TlPb2Br5-x I x quaternary system.

Developing X-ray and γ-ray detectors with stable operation at ambient temperature and high energy resolution is an open challenge. Here, we present an approach to search for new detector materials, combining binary photodetector compounds. More specifically, we explore quaternary TlPb2Br5-x I x compositions, relying on materials synergy between TlBr, TlI, and PbI2 photodetectors. We discover a broad solid solution in the TlPb2Br5-'TlPb2I5' section, which can be derived from a new quaternary compound, TlPb2BrI4, by partial substitution of Br by I atoms on the 4c site or by replacement of I by Br atoms on the 16l site. We carry out a thorough crystallographic analysis of the new TlPb2BrI4 compound and prepare a high-quality standardized structure file. We also complete the phase diagram of the TlPb2Br5-'TlPb2I5' section, based on 21 alloys. Furthermore, we synthesize a series of high quality centimeter-sized TlPb2Br5-x I x single crystals (x = 2, 2.5, 3, 3.5, 4, 4.5) by the Bridgman-Stockbarger method and study their structure and properties using a combination of experimental techniques (X-ray diffraction, X-ray photoelectron spectroscopy, and absorption spectroscopy) and theoretical calculations.

Photoelectrical properties and the electronic structure of Tl(1-x)In(1-x)Sn(x)Se2 (x = 0, 0.1, 0.2, 0.25) single crystalline alloys.

Photoelectrical properties of Tl1-xIn1-xSnxSe2 single crystalline alloys (x = 0, 0.1, 0.2, 0.25) grown using the Bridgman-Stockbarger method were studied. The temperature dependence of electrical and photoconductivity for the Tl1-xIn1-xSnxSe2 single crystals was explored. It has been established that photosensitivity of the Tl1-xIn1-xSnxSe2 single crystals increases with x. The spectral distribution of photocurrent in the wavelength spectral range 400-1000 nm has been investigated at various temperatures. Photoconductivity increases in all the studied crystals with temperature. Therefore, thermal activation of photoconductivity is caused by re-charging of the photoactive centers as the samples are heated. Based on our investigations, a model of center re-charging is proposed that explains the observed phenomena. X-ray photoelectron valence-band spectra for pristine and Ar(+)-ion irradiated surfaces of the Tl1-xIn1-xSnxSe2 single crystals have been measured. These results reveal that the Tl1-xIn1-xSnxSe2 single-crystal surface is sensitive to the Ar(+) ion irradiation that induced structural modification in the top surface layers. Comparison on a common energy scale of the X-ray emission Se Kß2 bands representing energy distribution of the Se 4p-like states and the X-ray photoelectron valence-band spectra was done.