van der Waals epitaxial growth of thin BiI3 films on PbI2 and CdI2 substrates by a hot wall method

Abstract

A hot wall technique was applied to grow very thin BiI₃ single crystals about 100–1000 Å thick by the achievement of low‐temperature growth. The so‐called van der Waals epitaxy became possible by employing layered materials such as PbI₂ and CdI₂ as substrate. BiI₃ thin films grown with optimized conditions exhibited a sharp band‐edge direct exciton absorption line of 30‐meV half‐width, which is much sharper than that of a single crystal grown by a conventional method reported so far. The transmission electron diffraction measurements were carried out on the films. It was revealed that highly perfect single crystals with a 4‐mm diameter size were obtained.