Submonolayer regime of Co epitaxy on Pd(111): Morphology and electronic structure

We report on the early stage of Cobalt growth on Pd(111) studied with scanning tunneling microscopy. The electronic structure of the islands grown at 550 and 300 K was studied with scanning tunneling spectroscopy at low temperatures. Triangular monolayer-high islands grown at 550 K show fcc or hcp stacking. The position and the intensity of the surface-state peak depend on the stacking of these islands. On the hexagonal double-layer islands grown at 300 K, a dislocation pattern appears, which contains atoms in fcc and hcp, as well as a dislocation line and top positions. Fcc and hcp regions show similar features in dI/dU spectra; however, the surface-state peak positions are slightly shifted. For these islands, spin-polarized STS measurements reveal a spin contrast reflecting perpendicular magnetization.