Subsurface growth of Ni atoms deposited on a Cu(001) surface

The growth of Ni deposited at room temperature on a Cu(001) surface was studied by low energy electron diffraction (LEED). For ultrathin Ni films, ranging from 1 monolayer (ML) to 3 ML, subsurface Ni layers below a 1 ML thick Cu surface layer were found to give the best fit to LEED I/V (intensity versus beam voltage) characteristics. For 1 ML thick Ni film, first-principles calculation also predicted that subsurface growth of Ni film was favored energetically to overlayer growth. As the film thickness increased, however, the reliability factor became worse. This indicated that the structure gradually deviated from the ideal subsurface Ni layer below 1 ML surface Cu. The deviation was possibly caused by the increasing disorder in the atomic structure and/or in the chemical homogeneity near the surface.