Growth of ferromagnetic dot arrays on Cu(0 0 1)–c(2×2)N surfaces

Growth of iron is studied on the nitrogen adsorbed Cu(0 0 1) surface, where 5×5 nm2 patches of N-adsorbed c(2×2) structure are squarely arranged and separated by a few nm wide clean Cu(0 0 1) surfaces. Mono-atomic layer Fe dots initially grow at the intersections of the clean Cu lines when the widths of the lines are smaller than 3 nm. The results are compared with the previous results on the growth of Ni and Co on the same surface. The position-selective nucleation of iron dots is ascribed to the difference in the surface strain caused by the presence of c(2×2)N patches; strain at the intersection is smaller than that at the middle of the narrow line. Similar explanation is applicable for Ni and Co growth although the detail of the selective growth depends on the species. On nitrogen-saturated Cu(0 0 1) surfaces as well, position-selective nucleation of iron dots is observed and the origin is also ascribed to the inhomogeneous surface strain.