Direct Growth of van der Waals Tin Diiodide Monolayers

Two‐dimensional (2D) van der Waals (vdW) materials have garnered considerable attention for their unique properties and potentials in a wide range of fields, which include nano‐electronics/optoelectronics, solar energy, and catalysis. Meanwhile, challenges in the approaches toward achieving high‐performance devices still inspire the search for new 2D vdW materials with precious properties. In this study, via molecular beam epitaxy, for the first time, the vdW SnI(2) monolayer is successfully fabricated with a new structure. Scanning tunneling microscopy/spectroscopy characterization, as corroborated by the density functional theory calculation, indicates that this SnI(2) monolayer exhibits a band gap of ≈2.9 eV in the visible purple range, and an indirect‐ to direct‐band gap transition occurs in the SnI(2) bilayer. This study provides a new semiconducting 2D material that is promising as a building block in future electronics/optoelectronics.