Wide-Bandgap Rare-Earth Iodate Single Crystals for Superior X-Ray Detection and Imaging.

Semiconductor-based X-ray detectors with low detectable thresholds become critical in medical radiography applications. However, their performance is generally limited by intrinsic defects or unresolved issues of materials, and developing a novel scintillation semiconductor for low-dose X-ray detection is a highly urgent objective. Herein, a high-quality rare-earth iodate Tm(IO 3 ) 3 single crystal grown through low-cost solution processing is reported with a wide bandgap of 4.1 eV and a large atomic number of 53.2. The roles of IO and TmO groups for charge transport in the Tm(IO 3 ) 3 are revealed with the structural difference between the [101] and [ 1 ¯ 01 ] $[{\bar{1}}01]$ crystal orientations. Based on anisotropic responses of material properties and detection performances, it is found that the [ 1 ¯ 01 ${\bar{1}}01$ ] orientation, the path with fewer IO groups, achieves a high resistivity of 1.02 × 10 11 Ω cm. Consequently, a single-crystal detector exhibits a low dark current and small baseline drifting due to the wide bandgap, high resistivity and less ion migration of Tm(IO 3 ) 3 , resulting in a low detection limit of 85.2 nGy air s -1 . An excellent X-ray imaging performance with a high sensitivity of 4406.6 µC Gy air -1 cm -2 is also shown in the Tm(IO 3 ) 3 device. These findings provide a new material design perspective for high-performance X-ray imaging applications.