Effect of impurities on the surface morphology of Fe(111)

► Sulfur-segregated Fe(111) surface exhibit numerous triangular pits of various sizes. ► A fractal of Sierpinski gasket is formed on S/Fe(111). ► N-segregated surface shows triangular clusters aligned in a hexagonal configuration. ► Cr film induces the formation of triangular pyramid-shaped CrN nanoclusters.