Growth, thermal stability and magnetism of Ni ultrathin films on O-3 × 3/W(1 1 1) surface

In this study, a well ordered O-3 × 3 superstructure was prepared on a W(1 1 1) surface for the investigation of the growth, thermal stability and magnetism of Ni ultrathin films on it. During the deposition and thermal annealing, Auger signal of oxygen was nearly invariant, indicating that the oxygen played a role of surfactant in this system. Due to the large lattice mismatch between the Ni films and W(1 1 1) substrate (3.95%), Ni underwent an island-growth, which was considerably affected by the growth temperature. After annealing at 500-800 K, the Auger signal ratio of Ni/W significantly decreased to approximately 1, indicating the formation of 3-dimensional islands with a wetting thickness of one pseudomorphic layer. Subsequent annealing to 800-1200 K annealing led to the more serious aggregation, i.e. de-wetting of Ni layer. The 3 and 11.5 PML Ni films revealed a stable canted magnetization, which was possibly attributed to the magneto-elastic anisotropy in the Ni films.