Reviewing polycrystalline mercuric iodide X-ray detectors

Polycrystalline films of HgI2, which are used as nuclear radiation detectors, are fabricated by two different methods, either by Physical Vapor Deposition (PVD) or glued with a polymeric binder called also "Particle in Binder" (PIB). Both types of PVD or PIB Detectors are deposited directly on Thin Film Transistor TFT technology imagers and can be used for X-ray imaging. The present review is concentrated on PVD- Polycrystalline-HgI2. However, the main review body is a summary of the work performed by RTR, HU, and Varian. Works by other groups are mentioned briefly. The PVD process is explained by reviewing X-ray Diffraction (XRD) and Scanning Electron Microscope (SEM) data. The charge transport properties of the PVD-Polycrystalline HgI2 detectors as they improved with R&D efforts are shown. The response of these PVD detectors to Am-241 and Co-57 gamma rays and their X-ray imaging properties such as dark currents, sensitivity, imaging resolution and Detector Quantum Efficiency (DQE) are reviewed.