Arrays of nanostructured antidot in Ni80Fe20 magnetic thin films by photolithography of polystyrene nanospheres

Ordered nanostructures consisting in arrays of nanopores and nanoholes in magnetic thin films have been the subject of intensive research. In this work, a novel multi-step lithography process based on self-assembling of polystyrene nanospheres is proposed to pattern arrays of nanoholes on a Ni80Fe20 thin film. Such a method allows antidot patterns to be fabricated on a wider area with respect to the standard sequential lithography. A polymeric mask is created by depositing a layer of polystyrene nanospheres on a photoresist subsequently exposed to a mercury lamp. The novelty in the procedure lies in exploiting low-cost and fast, non-sequential optical lithography with enhanced spatial resolution. Arrays of holes having mean size ranging in the interval of 250-280 nm depending on the experimental conditions have been prepared in Ni80Fe20 films of different thickness (between 20 and 60 nm). Sample morphology has been checked by scanning electron microscopy. Magnetic and magnetotransport properties have been measured as a function of temperature on films of different thickness. An anisotropic magnetoresistance effect has been observed in all patterned films independent on the film thickness. This result, similar to the ones reported for patterned nanostructure obtained with conventional lithography techniques, confirms the potential of the proposed technique.

► Arrays of antidot in Ni80Fe20 thin films by photolithography of polystyrene nanospheres. ► Well-ordered Antidot arrays on a large scale. ► Novel method exploiting optical lithography with enhanced spatial resolution. ► We report on the presence of an anisotropic magnetoresistance signal.