The influence of substrate preoxidation on the growth of Ni on Cu(1 1 0)

The growth of ultrathin Ni films on a O-(2 × 1)-reconstructed Cu(1 1 0) single crystal is compared to the one of Ni on clean Cu(1 1 0). Scanning tunneling microscopy and low energy electron diffraction reveals that the O atoms float on top of the growing Ni film leading to a (2 × 1)-symmetry. The floating O layer is found to influence the growth mode of the system significantly. At low coverages O changes the preferential growth direction of the Ni islands, which is reflected in a rotation of the island edges by 90°. At higher coverages the O is found to reduce the surface roughness compared to films deposited on the clean Cu(1 1 0) surface, thus acting as a surfactant.