Lattice distortion of square iron nitride monolayers induced by changing symmetry of substrate

Rectangular iron nitride monatomic layers are fabricated on the threefold symmetric Cu(111) substrate by taking advantage of the stability of the square nitride film. Two different ordered structures are observed on the Cu(111) substrate by scanning tunneling microscopy after annealing at 510 K and 580 K. Their chemical composition and lattice symmetry are investigated by x-ray photoelectron spectroscopy and low energy electron diffraction. The monolayer film prepared at 580 K is a distorted ${\mathrm{Fe}}_{2}\mathrm{N}$ monolayer analogous to a ferromagnetic square ${\mathrm{Fe}}_{2}\mathrm{N}$ monolayer with a clock reconstruction on the Cu(001) substrate. The lattice deformation of the square ${\mathrm{Fe}}_{2}\mathrm{N}$ monolayer is induced by using Cu(111) with threefold symmetry.