Van der Waals epitaxy of metal dihalide

Ultrathin layered metal dihalide films (PbI2, CdI2) were grown on highly lattice mismatched (max. 44%) surfaces of several layered materials (LMʹs) and their growth features were studied by reflection high energy electron diffraction. Those metal dihalides grew epitaxially with their (0001) surfaces parallel to those of the substrates. They have their own bulk lattice constants even from the initial stage of growth in spite of a large lattice mismatch with the substrate, in a similar way as the epitaxial growth between the LMʹs hitherto investigated. It has been found that the in-plane axes of metal dihalides align with one of the main crystal axes of the substrates so as to minimize incommensurateness, which indicates that the lattice constant ratio between an overgrown and a substrate materials is a determining factor for the in-plane orientation in van der Waals epitaxy.