Coverage dependent atomic structures of copper nitride on Cu(111)

Earth abundant transition metal nitrides represent an emerging class of heterogeneous catalysts and catalyst supports. However, understanding of surface atomic structure remains limited, partially due to the challenges in synthesizing nitrides on single crystal surfaces. In this work, an ion source is used to directly ionize molecular nitrogen and synthesize nitrogen covered Cu(111) surfaces. Regulation of surface nitrogen coverage via annealing temperature enables systematic characterization by scanning tunneling microscopy at an atomic level. Copper nitride species form a square pattern corresponding to the Cu3N(100) monolayer, undergo a transformation from square to hexagonal assemblies, and appear as adatoms at step edges and on terraces. These results elucidate the evolution of copper nitride surface structures and demonstrate a potentially general method for synthesizing transition metal nitrides on earth abundant single crystal surfaces.