Nanostructures made by mixing Rh atoms on N-adsorbed Cu(001) surface

Nanostructures and nanopattern formation by mixing Rh atoms were studied on the N-saturated Cu(001) surface using scanning tunneling microscopy and X-ray photoemission spectroscopy. Most of the Rh atoms are in the topmost layer of the surface, and make a line structure of two atomic width in the <100> direction. Each Rh atom in the line is bonded to one N atom. The density of trench-like structures at the N-saturated surface decreases with increasing the density of the lines. This indicates that the line structure reduces the surface stress induced by N adsorption. When the Rh atoms cover more than a quarter of surface on average, the lines form a rectangular pattern at the surface. The average separation decreases with the increase of the Rh density, and is 4 nm for the 30% Rh coverage. The pattern formation is attributed to the efficient reduction of lattice strain as the grid pattern on the partially N-adsorbed Cu(001) surface.