Single-crystal growth of HgI₂ and its characterizations

α-HgI₂ single crystal was grown by vapor sublimation method within a vertical transparent two-zones growth furnace. In the primary growth stage, HgI₂ shows a faceted growth interface, which finally changes into the spherical one due to the high thermal resistance of HgI₂. XRD, UV-VIS-IR spectrum and I-V analysis were used to characterize the properties of the as-grown crystal. The results of XRD show that the as-grown crystal is a single α-HgI₂ phase with the growth direction of [001]. The UV-VIS-IR spectrum indicates that the energy gap of α-HgI₂ is about 2.12 eV, corresponding to the wavelength of 580 nm. Near-infrared transmittance of HgI₂ is about 45%. Two absorption peaks were observed at the wavelength of 2307.5 nm and 1731.4 nm due to the absorption of the cavity and trap levels. The electrical resistivity of the wafers was determined by I-V characteristic to be about 1011 Ω·cm.