MnBr 2 ${\rm MnBr}_2$ on the Graphene on Ir(110) Substrate: Growth, Structure, and Super-Moiré

Single-layer ${\mathrm{MnBr}}_2$ is grown on graphene (Gr) supported by Ir(110) and investigated using low-energy electron diffraction, scanning tunneling microscopy, and spectroscopy. The structure and epitaxial relationship with the substrate are systematically characterized. The growth morphology strongly depends on the growth temperature, evolving from fractal to dendritic and eventually to compact dendritic-skeletal islands, reflecting changes in the underlying surface diffusion processes. The pronounced variation in the apparent height with tunneling conditions for the magnetic insulator is explained based on the measured electronic density of states. ${\mathrm{MnBr}}_2$ on Gr/Ir(110) constitutes a three-lattice system, giving rise to a super-moiré pattern - a moiré of moirés. The super-moiré of ${\mathrm{MnBr}}_2$ /Gr/Ir(110) is unique, as it involves a virtual moiré of ${\mathrm{MnBr}}_2$ with the Ir(110) surface lattice - two lattices not in contact with each other. Using a careful Fourier analysis, the known properties of Gr/Ir(110), and the results of ab initio calculations, the origin of the virtual moiré is uncovered and related to the inhomogeneous binding of Gr to Ir(110). Comparative experiments with ${\mathrm{MnBr}}_2$ on Gr/Ir(111) show similar growth and structure, but highlight the unique properties of the ${\mathrm{MnBr}}_2$ /Gr/Ir(110) super-moiré.