<title>Mercuric iodide polycrystalline films</title>

Abstract

Mercuric iodide (HgI₂) polycrystalline films are being developed as a new detector technology for digital x-ray imaging. Films have been grown with areas up to 80 cm² (4' diameter) and thickness of 20-250 micrometers using sublimation. The growth techniques used can be easily extended to produce much larger film areas (>10'x10'). Thickness of the grown layers and size of the grains can be regulated over a wide range by adjusting the growth parameters. The films were characterized with respect to their electrical properties and in response to ionizing radiation. Leakage current as low as 40 pA/cm² at the operating bias voltage of ~50 V has been observed. High sensitivity and excellent linearity in the response to x-rays was measured. Signals from these 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. The low dark current, good sensitivity, and linearity of the response to x-rays put HgI₂ polycrystalline semiconductor detectors in position as a leading candidate material for use in digital x-ray imaging systems. Our future efforts will concentrate on optimization of film growth techniques specifically for deposition on a-Si:H flat panel readout arrays.