Magnetic and structural properties of Ni nanocaps deposited onto self assembled nanosphere array

Magnetic, structural and morphological results are presented on Ni (40 nm) thin film deposited on self assembled polystyrene (PS) nanosphere arrays by molecular beam epitaxy and the observed properties are compared with the results obtained on the similar film simultaneously deposited on Si and GaAs substrates prepared under the same environment. These nanospheres produce good uniformity over a large area as clearly seen in a scanning electron microscopy image. The Ni film grown on these nanospheres is polycrystalline in nature with grain size of ~ 7.5 nm. Corresponding magnetic force microscopy measurements confirm the influence of substrate material on magnetic domains in the samples. A comparatively higher coercivity of ~ 23 mT is observed by magneto optical Kerr effect measurement performed on Ni (40 nm)/PS, while the coercivities of Ni/Si and Ni/GaAs reference films are only ~ 13 mT and ~ 15 mT respectively. The observed results are interpreted in terms of influence of substrate and growth morphology on the magnetic properties of Ni films.