Fabrication and properties of superhydrophobic SiO2 thin film by sol-gel method

Superhydrophobic SiO2 thin films were successfully fabricated on a glass substrate by sol-gel method. To fabricate SiO2 thin film with a high roughness, SiO2 nano particles were added into tetraethoxysilane (TEOS) solution. The prepared SiO2 thin film without an addition of SiO2 nano particles showed a very flat surface with ca. 1.27 nm of root mean square (RMS) roughness. Otherwise, the SiO2 thin films fabricated by using coating solutions added SiO2 nano particles of 1.0, 2.0 and 3.0 wt% showed a RMS roughness of ca. 44.10 nm, ca. 69.58 nm, ca. 80.66 nm, respectively. To modify the surfaces of SiO2 thin films to hydrophobic surface, a hydrophobic treatment was carried out using a fluoroalkyltrimethoxysilane (FAS). The SiO2 thin films with a high rough surface were changed from hydrophilic to hydrophobic surface after the FAS treatment. Especially, the prepared SiO2 thin film with a RMS roughness of 80.66 nm showed a water contact angle of 163 degrees.