Structure of highly strained ultrathin Ni films on Pd(1 0 0)

The epitaxial growth of ultrathin Ni films on the Pd(1 0 0) surface was studied by means of XPS, angle-scanned photoelectron diffraction (XPD) and LEED experiments. The XPD and LEED data indicate that the early stages of deposition are characterised by the formation of a tetragonally strained Ni fcc phase, which subsequently develops into a bulk-like Ni fcc structure as the critical thickness of approximately 12 MLeq is exceeded. The highly strained structure below the critical thickness is associated with subtle electronic structure changes with respect to Ni bulk, as evidenced by the analysis of the satellite structure in the Ni 2p XPS region.