Transparent superhydrophobic surfaces with high adhesion generated by the combination of femtosecond laser structuring and wet oxidation

In this work we demonstrate a fabrication process for the generation of quartz surfaces showing both high transparency and superhydrophobic behaviour. A thin a-Si layer on a quartz wafer was selectively structured by a femtosecond laser. After laser structuring the sample was thermally (wet) oxidized at 1100° until the a-Si layer was fully converted to SiO2. Since SiO2 is hydrophilic, an assistant layer was used to shift the contact angle of the material to a value higher than 90°. A thin layer of Teflon-like polymer was deposited by a plasma process onto the oxidized SiO2 surface. With this process chain it is possible to generate a functional surface with a water contact angle (CA) of up to 163° combined with high transparency close to 80% and a high adhesion with a CA hysteresis of up to 151°.