Examination of HgI2 and PbI2 photoconductive materials for direct detection, active matrix, flat-panel imagers for diagnostic X-ray imaging

In this paper, the results of initial empirical studies of the dark current and X-ray signal response of thick, polycrystalline films of lead iodide (PbI₂) and mercuric iodide (HgI₂) are reported. These studies are being carried out as part of an extensive, integrated program of research to develop and incorporate such photoconductive, X-ray detection materials into direct detection, active matrix flat-panel imagers (AMFPIs) for applications in diagnostic imaging, as well as for radiotherapy imaging. Simple detector configurations incorporating these materials were prepared by physical vapor deposition (PVD) with thicknesses ranging from approximately 90 to 500 urn. In the present study, dark current, X-ray sensitivity and temporal response of the detectors were quantitatively evaluated under irradiation conditions relevant to radiography, fluoroscopy and mammography. Measurements were performed for externally applied bias voltages ranging from 0.1 to 2.0V/μm for both negative and positive polarities.