Sensitive and Fast Direct Conversion X‐Ray Detectors Based on Single‐Crystalline HgI₂ Photoconductor and ZnO Nanowire Vacuum Diode

Abstract Photoconductive cold cathode X‐ray detectors are highly promising for use in medical diagnosis, industrial inspection, and scientific research applications. However, development of highly sensitive, fast, and stable direct conversion X‐ray detectors remains very challenging because of structural and material limitations. This article presents a direct conversion X‐ray detector based on a HgI₂ crystal and a ZnO nanowire vacuum diode with sensitivity of 6.8 × 10³ µCGy_air⁻¹ cm⁻², which is nearly two orders of magnitude higher than that of a commercial a‐Se X‐ray detector. The X‐ray detector, which uses a high‐crystallization HgI₂ photoconductor, shows a response time of 0.24 ms, thus significantly outperforming the polycrystalline HgI₂ X‐ray detector. In addition, the current limitation between the HgI₂ photoconductor and the ZnO nanowire cold cathodes guaranteed device reliability under high applied electric fields for practical applications. The findings presented in this work demonstrate that the proposed X‐ray detector based on the HgI₂ photoconductor and the ZnO nanowire vacuum diode is highly efficient and stable.