Surface morphology of ferromagnetic nickel thin films on polyethylene naphtalate organic films for spin quantum cross structures

We investigated surface morphologies of Ni thin films evaporated on polyethylene naphtalate (PEN) organic substrates for the fabrication of spin quantum cross structures and discussed its feasibility toward ferromagnetic nanojunctions from a viewpoint of the Ni grain size and the Ni surface roughness. The grain size for Ni films of sub-10-nm thickness is ∼30 nm, which is larger than the Ni thickness, and the surface roughness, in the scanning scale of the film thickness, is less than 0.25 nm, corresponding to one-atomic-layer thickness. These experimental results indicate that spin quantum cross structures which consist of Ni thin films on PEN substrates can be expected as a candidate of ferromagnetic nanojunctions, which may lead to large magnetoresistance effect.