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Micromachines 2018, 9(8), 389; https://doi.org/10.3390/mi9080389

Glancing Angle Deposition Effect on Structure and Light-Induced Wettability of RF-Sputtered TiO2 Thin Films

1
Department of Chemical Engineering, University of Patras, GR-26504 Patras, Greece
2
Department of Mechanical Engineering, Technological-Educational Institute of Western Greece, GR-26334 Patras, Greece
3
Department of Chemistry, University of Ioannina, GR-45110 Ioannina, Greece
4
Institute of Chemical Engineering Sciences/FORTH, P.O. Box 1414, GR-26504 Patras, Greece
*
Author to whom correspondence should be addressed.
Received: 13 June 2018 / Revised: 19 July 2018 / Accepted: 31 July 2018 / Published: 4 August 2018
(This article belongs to the Special Issue Plasma-Based Surface Engineering)
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Abstract

Crystalline TiO2 films were prepared on unheated glass substrates by radio frequency (RF) reactive magnetron sputtering at normal angle of incidence (a = 0°) and at glancing angle (a = 87°). The effect of the glancing angle on the structure, microstructure, and wetting properties of the films was investigated. The inclination of the substrate led to phase transformation of the deposited films from rutile to either rutile/anatase or anatase, depending on the working pressure. Extreme shadowing at 87° results in a remarkable increase of the films’ porosity and surface roughness. The mechanism of the glancing-angle-induced crystalline phase formation is thoroughly discussed based on the thermodynamic, kinetic, and geometrical aspects of the nucleation and is related with the microstructural changes. Both crystalline phase and microstructure significantly affect the wetting properties of the TiO2 films. Glancing-angle-deposited anatase TiO2 exhibits a high degree of porosity and roughness, a high rate of UV-induced wettability conversion, and a long-term highly hydrophilic nature in dark. Therefore, anatase TiO2 is potentially a good candidate for applications as dye-sensitized solar cells (DSSC)/perovskite solar cells, microfluidic devices, and self-cleaning surfaces prepared on thermosensitive substrates. View Full-Text
Keywords: sputtering; glancing angle; TiO2; superhydrophilic; hydrophilic; anatase; rutile; GLAD; porous titania sputtering; glancing angle; TiO2; superhydrophilic; hydrophilic; anatase; rutile; GLAD; porous titania
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
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Vrakatseli, V.E.; Kalarakis, A.N.; Kalampounias, A.G.; Amanatides, E.K.; Mataras, D.S. Glancing Angle Deposition Effect on Structure and Light-Induced Wettability of RF-Sputtered TiO2 Thin Films. Micromachines 2018, 9, 389.

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