Wei Li,Yalun Xu,Jiali Peng,Ruiming Li,Jiannan Song,Huihuang Huang,Lihao Cui,Qianqian Lin
X-ray detection is widely utilized in our daily life, such as in medical diagnosis, security checking, and environmental monitoring. However, most of the commercial X-ray detectors are based on inorganic semiconductors, e.g., Si, CdTe, and Ge, which require complex and costly fabrication processes. Metal halide perovskites have recently emerged as a set of promising candidates for ionizing radiation detection, owing to the high attenuation coefficient, long carrier lifetime, and excellent charge transport properties. Perovskite single crystals have been successfully implemented in X-ray detection, but the fragile single crystals limit the device fabrication and the integration with a read-out circuit. In addition, it is hard to reach inch-size single crystals for real application. Flexible devices based on perovskite films or composite films have also been reported, but either the thickness or charge transport properties are limited by the solution processes. In this work, we introduced thermal co-evaporation to deposit highly efficient formamidinium lead iodide perovskite films. Considering the trade-off between X-ray absorption and charge transport, we optimized the active layer thickness and achieved large-area and flexible X-ray detectors with state-of-the-art device performance, including extremely low dark current and noise, fast response, and high sensitivity of 142.1 μC Gyair–1 cm–2.
Single-crystal p-type ZnSe nanowires (NWs) with zinc blende structure and [21–1] growth direction were synthesized by using bismuth (Bi) as dopant via a thermal co-evaporation method. The ZnSe : Bi NWs showed evident p-type conductivity with hole concentration up to 4.1 × 1018 cm−3 after the acceptor activation. Negative photoconductivity was first investigated in the p-ZnSe NWs, i.e., the conductivity of the NWs under light was dramatically lower than that in the dark. Surface effects arising from oxygen absorption and photo-desorption were suggested to be responsible for this. By using Al as the Schottky gate, high-performance nano-metal-semiconductor field-effect transistors (nanoMESFETs) were constructed, and measurements on the Al/p-ZnSe NW Schottky diode also revealed the bias-dependent photoresponse. It is expected that the p-type ZnSe : Bi NWs will have great potential in nano-optoelectronic applications.
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