Tetragonal mercuric iodide, as a group of wide band gap semiconductors, has been widely
investigation during most of the last half-century, applied on room-temperature X-ray and gamma-ray
spectrometers. Up to the present, Mercuric iodide (HgI<sub>2</sub>) is still thought to be one of the most outstanding
vitality semiconductor materials because of its wide band gap, for which the device was required to be
high resistivity, high atomic number, adequate mechanical strength, long carrier lifetimes and high
mobility-lifetime produces. Now, HgI<sub>2 </sub>polycrystalline films are being developed as a new detector
technology for digital x-ray imaging. In this research, HgI<sub>2</sub> polycrystalline films with different surface
areas of 1 and 36 cm<sup>2</sup> were grown by vapor sublimation method within a self-design growth furnace.
XRD, SEM and J-V analysis were used to characterize the properties of these as-grown films. The results
of XRD show that the ratio of (001) / (hkl) on all as-grown films is amount to be 90% for the area of 1 cm<sup>2</sup>
films. Grain size of 1 cm<sup>2 </sup>films was measured to be 120-150 μm. Their electrical resistivity were also
determined to be about 10<sup>11</sup> Ω·cm operated at the bias voltage of ~100 V by I-V characteristic
measurement. Utilizing the polycrystalline film with the area of 36 cm<sup>2</sup> deposited on TFT, we then
prepared the direct image detector after capsulation for non-corrosive steel screw imaging. The results
indicated that profile of screw was distinctly exhibited in digital x-ray imaging systems.