Characterization of strain and crystallographic defects in HgI2 single crystals

We investigated bulk-grown HgI2 crystals to better understand the nature of crystallographic defects and strain/stress in different growth regions of the crystal and their affect on the performance of HgI2-based radiation detectors. Double-axis and triple-axis high-resolution x-ray diffraction were used to characterize the mosaic structure and strain in HgI2. Rocking curves revealed significant mosaic spreading in <110> growth regions exhibiting X-defects versus X-defect-free <100> growth regions. Both <110> and <100> growth regions exhibited little strain (similar to0.01%). We report the narrowest rocking curves (similar to9 arcsec) to date on HgI2 as a result of the resolution of the instrument (similar to6 arcsec). Raman spectroscopy was used collaboratively to confirm little residual stress in the crystals. We developed a growth rate ratio (X) and show this geometric model used to describe crystal shape and regions of <100> and <110> growth. Optical characterization of X-defects are presented and discussed. Further the influence of crystallographic defects and strain on radiation detector performance are discussed.