Study on growth of large area mercuric iodide polycrystalline film and its x-ray imaging

Abstract

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 (HgI₂) 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, HgI₂polycrystalline films are being developed as a new detector technology for digital x-ray imaging. In this research, HgI₂ polycrystalline films with different surface areas of 1 and 36 cm² 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 cm² films. Grain size of 1 cm²films was measured to be 120-150 μm. Their electrical resistivity were also determined to be about 10¹¹ Ω·cm operated at the bias voltage of ~100 V by I-V characteristic measurement. Utilizing the polycrystalline film with the area of 36 cm² 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.