HgI2 polycrystalline films for digital X-ray imagers

This paper describes recent results obtained with mercuric iodide (HgI2) polycrystalline films that we have produced. The ultimate goal of this effort is to develop a new detector technology for digital X-ray imaging based on HgI2 polycrystalline films coupled to large-area flat-panel amorphous silicon, thin-film transistor-addressed readout arrays. We have employed two approaches for producing the polycrystalline films: 1) thermal evaporation (sublimation) and 2) deposition of films from various solutions. The 50- to 150-mum-thick films were characterized with respect to their electrical properties and in response to ionizing radiation. The leakage current was about 40 pA/cm(2) at an operating bias voltage of similar to50 V. Signals from the HgI2 polycrystalline detectors, in response to ionizing radiation, compare favorably to the best published results for all high Z polycrystalline films grown elsewhere, including TlBr, PbI2, and HgI2.