Fabrication of size-tunable hierarchical CrN nanohole arrays for two-dimensional nanomould using modified nanosphere lithography

This Letter presents a low-cost, high-throughput strategy for fabricating size-tunable hierarchical CrN nanohole arrays for a nanomould using a magnetron sputtering approach with nanosphere lithography (NIL)-based technology. The size of the polystyrene nanospheres has a direct influence on the diameter and period of the CrN nanohole structure. The reactive ion etching and magnetron sputtering process can easily control the nanohole size and depth. The hole depth generally depends on the film thickness. The contact angles were measured by the sessile drop method using distilled water, ethylene glycol and diiodomethane. The surface-free energy of the CrN nanomould was calculated using the Owens-Wendt geometric mean approach. This Letter reports the successful fabrication of a series of nanoholes with diameters decreased from 347 ± 9.6 to approximately 166 ± 11.8 nm with a depth of 100 ± 5.6 nm. The corresponding surface-free energy decreased from 40.83 to approximately 24.58 mN/m. The diameter of nanoholes has an obvious effect on the surface-free energy and there is tendency for the surface-free energy to decrease with the decrease in the diameter of the nanoholes. This new approach of ordered CrN nanohole array structures can be used to create a two-dimensional nanomould for NIL.