Rapidly switched wettability of titania films deposited by dc magnetron sputtering (original) (raw)
Related papers
Micromachines
Transparent polycrystalline TiO2 thin films have been deposited on unheated glass substrates using RF reactive magnetron sputtering. Depositions were carried out at different glancing angles and with different total gas mixture pressures. The variation of these parameters affected the crystal phase composition and the surface morphology. Depending on the glancing angle and the pressure, rutile, mixed anatase/ rutile and pure anatase were deposited at low substrate temperature. Both hydrophilic and hydrophobic TiO2 were obtained, exhibiting fast photoconversion to superhydrophilic upon UV irradiation. The effect of the materials physicochemical properties on the wettability and rate of the UV induced superhydrophilicity is evaluated.
Crystalline TiO2 films were prepared on unheated glass substrates by RF reactive 15 magnetron sputtering at normal angle of incidence (a=0 o) and at glancing angle (a=87 o). The effect 16 of the glancing angle on the structure, microstructure and wetting properties of the films is 17 investigated. The inclination of the substrate led to phase transformation of the deposited films 18 from rutile to either rutile/anatase or anatase, depending on the working pressure. Extreme 19 shadowing at 87 o results in remarkable increase of the films porosity and surface roughness. The 20 mechanism of the glancing angle induced crystalline phase formation is thoroughly discussed, 21 based on the thermodynamic, kinetic and geometrical aspects of the nucleation and is related with 22 the microstructural changes. Both crystalline phase and microstructure affect significantly the 23 wetting properties of the TiO2 films. Glancing angle deposited anatase TiO2 exhibits high degree of 24 porosity and roughness, high rate of the UV induced wettability conversion and a long term 25 highly hydrophilic nature in dark. Therefore, anatase TiO2 is potentially a good candidate for 26 applications as dssc's/perovskite solar cells, microfluidic devices and self-cleaning surfaces 27 prepared on thermosensitive substrates. 28