Atomic structure of interface between monolayer Pd film and Ni(111) determined by low-energy electron diffraction and scanning tunneling microscopy

The atomic structure of Pd ultrathin films grown on Ni(111) at 300 K is investigated by low-energy electron diffraction and scanning tunneling microscopy. It is determined atomically that the growth of monolayer Pd films leads to a periodic arrangement of triangular misfit dislocation loops in the underlying Ni(111) surface, resulting in a triangular superstructure on the monolayer Pd surface. The triangular dislocation loops tend to align at an angle of about 5° from the Ni atom row, owing to a slight rotation of the Pd films with respect to the Ni substrate, and appear as a moirelike superstructure on the multilayer Pd surfaces. Atomistic simulations indicate that the slight rotation of monolayer Pd films and the formation of misfit dislocation loops in the Ni surface minimize the Pd–Ni interface energy.