Hydrophobic surface modified HfO 2 antireflective coatings

A multifunctional antireflective (AR) thin film is always a prerequisite for growing high-tech applications. Herein we proposed a surface modification technique to transform the hydrophilic behaviour of HfO 2 AR nanofilms into hydrophobic without influencing the nanostructure, morphology, refractive index ( η ) or AR efficacy of HfO 2 nanofilms. Our experimental results demonstrate that the fabricated HfO 2 AR nanofilms retain its AR efficiency after surface modification to <1% in the visible wavelength range (450–700 nm) on FTO and sapphire. HfO 2 AR nanofilms show hydrophilic behaviour before surface modification with a water contact angle (WCA) of 29° on FTO and 22° on sapphire. However, after surface treatment, they display hydrophobic nature θ w > θ > 90° with a contact angle of (127°–130°). The experimental result demonstrates that the η of the thin layers fabricated at deposition angle 0°, 80°, and 88° before and after modification remains almost the same. HfO 2 AR nanofilms exhibit long term AR permanency as AR efficiency measured within a year practically displays the equivalent reflectance curves similar to as deposit AR thin films, i.e. <1% in the wavelength range of 450–700 nm. We proposed a cost-effective procedure to make hydrophilic AR films to show non-wetting behaviour for its long-term exposure in a moist, damp environment without affecting the refractive index of AR thin film.