Ultrasmooth Ni thin films evaporated on polyethylene naphthalate films for spin quantum cross devices

Surface morphology of Ni thin films vacuum-deposited on polyethylene naphtalate (PEN) organic films has been investigated as a function of Ni film thickness for spin quantum cross devices. The surface roughness of the Ni films decreases from 1.3 nm, being the roughness of PEN films, down to 0.69 nm as the thickness of Ni films increases up to 41 nm. As a result of the scaling investigation of the surface roughness, the surface roughness for Ni films of sub- 10-nm thickness, in the scanning scale of the film thickness, is less than 0.23 nm, corresponding to one atomic layer thickness. These experimental results indicate that Ni thin films on PEN films are suitable as a candidate of metal/insulator hybrid materials used for spin quantum cross devices and may open up a novel research field on the electric characteristics of a few atoms or molecules, which leads to high-density memories.