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 Gy_air^-1 cm^-2 and a low detection limit of 85 nGy_air 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.