Bismuth tri-iodide – Graphene 2D material

Abstract

In recent years, a multitude of 2D materials has been extensively studied, and new ones continue to emerge. Among these, bismuth tri-iodide-graphene material has been reported in both theoretical and experimental studies, displaying intriguing properties. These findings suggest potential photovoltaic applications for BiI3 layers and van der Waals superstructures. In this context, the present work explores the growth of van der Waals superstructures BiI3–graphene, obtained through physical vapor deposition. These structures are achieved by nucleating BiI3 and allowing it to grow on graphene-covered TEM grids and ultra-flat silicon substrates.When the structures are directly grown on grids and substrates covered with graphene, twisted BiI3 structures are formed, leading to Moiré interference, indicating the presence of two or more BiI3 layers and non-uniformity. However, when the structures are grown on grids pre-treated with UV/O3, and then subjected to annealing and post-growth, they become more uniform and aligned, without observable twisting. Structures obtained on substrates with this treatment and post-growth result in thinner layers, as thin as 7.59 ± 0.16 nm, with a roughness of 0.435 ± 0.018 nm. As the thickness decreases, the position of the (003) reflection peak in the diffraction pattern shifts to lower values and broadens, indicating an expansion of the cell along the c-axis. The obtained bandgap values, ranging from 1.55 ± 0.04 to 1.62 ± 0.04 eV, closely align with theoretical predictions. The obtained structures become part of the 2D universe of other similar materials, such as TMDs-graphene, and open up exciting possibilities for new properties and applications.