Molecular beam epitaxy growth of iodide thin films

Study of two-dimensional (2D) magnetic materials is important for both fundamental research and application. Here we report molecular beam epitaxy growth of iodides, candidates for exhibiting 2D magnetism. Decomposition of CrI₃ is utilized to produce stable gaseous I₂ flux. Growth of MnI₂, GdI₃, and CrI₂ down to monolayer is successful achieved by co-depositing I₂ and corresponding metal atoms. The thin films of the three materials are characterized by scanning tunneling microscope and found to be insulators with bandgaps of 4.4 eV, 0.6 eV, and 3.0 eV, respectively. The film growth paves the way for further study of magnetic properties at the 2D limit.