Some sources of defects in α-HgI2, the room temperature γ-ray detector

In the course of a systematic optimization of the materials properties of α-HgI₂ crystals for room temperature γ- and X-ray detectors, we have investigated possible sources of defects and discuss briefly the possibility to supress them. Due to the particular structure of α-HgI₂, large amount of impurities, particularly hydrocarbons, can be absorbed invan der Waals layers and lattice channels. Purification by sublimation does not work due to the affinity of hydrocarbons to iodine and their easy re-absorption in the sublimate. “Lattice filtering” of the large concentration of hydrocarbons contained even in “suprapure” iodine has been performed using the close spaced lattice of CuI. Oxidation of hydrocarbons by reaction of oxygen with HgI₂ is another possibility for their removal.