Single Crystal CdSe X-ray Detectors with Ultra-High Sensitivity and Low Detection Limit.

CdSe single crystals (SCs), with a relatively high atomic number, large X-ray absorption coefficients, and high carrier mobility, are expected to provide high-performance detection for X-ray. However, the difficulty of growing high-quality CdSe SC has severely limited its application in X-ray detection. In this work, we develop an unconstrained physical gas phase method and in situ annealing process to grow high-quality CdSe SCs under unconstrained conditions. Using this method, CdSe SCs exhibit natural exposure planes, ultrahigh resistivity of 5.43 × 1012 to 1.29 × 1013 Ω cm and high μτ product of 1.3 × 10-2 to 1.5 × 10-2 cm2 V-1. It is also observed that CdSe SC X-ray detectors exhibit a record sensitivity of 2.08 × 105 μC Gyair-1 cm-2 and a low detection limit of 85 nGyair s-1, which are both desired in medical diagnostics. Moreover, those devices with different crystal directions provide anisotropic X-ray detection performance. Our findings pave a new avenue to exploit high-performance CdSe SC X-ray detectors.