Abstract: Bismuth based halide materials show great potential because of their non-toxic and excellent photoelectric properties. As a layered heavy metal semiconductor, BiI₃ has been used in X-ray detection, γ-ray detection and pressure sensor. Recently it attracted much attention as an absorbing material for thin film solar cells. In this paper, a simple vapor transport deposition (VTD) method is used to obtain high-quality BiI₃ films with preferred c-axis orientation on glass substrate using BiI₃ crystal powder as evaporation source. By studying the effects of evaporation source temperature and deposition distance on the phase and morphology of BiI₃ thin films, the mechanism of preferential growth of BiI₃ thin films was proposed. The results show that the BiI₃ thin film prepared by VTD method belongs to triclinic crystal system, and its optical band gap is ~1.8 eV. The deposition temperature has a great influence on the preferred orientation of the films. When the deposition temperature is lower than 270 ℃, the deposited thin films have the characteristics of preferred orientation growth along the c-axis. Beyond this temperature, the c-axis preferential orientation is not observed. When the substrate temperature is 250 ℃ and the deposition distance is 15 cm, the thin films have the highest crystallanity and octahedral morphology.

Key words: BiI₃, vapor transport deposition, thin film, preferred orientation, growth mechanism, semiconductor, two-dimensional material