PhD Thesis Defence Presentations - Βασιλική Ελευθερία Βρακατσέλη
Titanium dioxide (ΤiO2) thin films have attracted immense attention during the last decades due to their unique properties (photocatalysis, photoinduced superhydrophilicity, biocompatibility and more) and their potential performance in energy (3rd generation thin film solar cells), optoelectronic and environmental applications. Their functionality largely depends on their crystalline structure and surface morphology, while between the TiO2 polymorphs, anatase and mixed anatase/rutile films are considered better photocatalysts than the rutile phase. However, the deposition of polycrystalline TiO2 films normally requires high substrate temperatures (>300oC) or post annealing of the films. This work explores the potential of RF reactive magnetron sputtering for the deposition of polycrystalline TiO2 films at low substrate temperature. For this reason, crystalline TiO2 deposition on cheap and versatile polymeric substrates is not always possible. Aiming to high quality functional TiO2 thin films, with the desired crystalline phase and morphology, different plasma parameters were implemented on two different geometries of the sputtering system: depositions on substrates at an offset distance from the sputtering source and on tilted substrates with respect to the source (glancing angle deposition, GLAD). Rutile, anatase and mixed phase anatase/rutile TiO2 films were obtained at low substrate temperature and with relatively high deposition rate. The effect of the deposition conditions on the film properties was evaluated by thorough characterization of the films in terms of structure, optical properties, microstructure and surface morphology by applying several characterization techniques. It was revealed that the glancing angle of the substrate and working pressure affect strongly both the structure and microstructure of the films. The deposited polycrystalline films wetting properties were also investigated and attributed to the synergistic effect of the crystal phase and surface topography. Finally, via an analysis of the deposition rate into high energy and low energy components and supplementary TEM studies on films growth, the mechanism of the low substrate temperature growth of rutile and anatase by RF magnetron sputtering is proposed.
Speakers Short CV (Σύντομο Βιογραφικό Ομιλητή)
Mrs Vasiliki Eleftheria Vrakatseli graduated from the Department of Chemical Engineering of the University of Patras in 2011. In 2012 she was admitted to the postgraduate program of the Department of Chemical Engineering, University of Patras and joined the research team of the Plasma Technology Laboratory. In the framework of her master's thesis, she was involved in the deposition of polymeric and inorganic thin films with special wetting properties by plasma processes and chemical deposition, while she also participated in the funded research project DESIREDROP in collaboration with NSCR Demokritos and the Technical University of Athens. In 2015 she obtained her postgraduate diploma in Materials Science and Technology, of the Department of Chemical Engineering, University of Patras, with a master's thesis entitled "Development of stable superhydrophilic films by plasma processes for use in microfluidic devices". She remained in the research team of the Plasma Technology Laboratory in order to conduct her PhD Thesis under the supervision of Professor Dimitrios Mataras, in which she was involved in the design and installation of a high vacuum RF magnetron sputtering system and in the development of functional titanium dioxide thin films.
- V.Vrakatseli, E.Farsari and D.Mataras (2020), Wetting properties of transparent anatase/rutile mixed phase glancing angle magnetron sputtered nano-TiO2 films, Micromachines, 11(6), 616
- V.E.Vrakatseli, A.N. Kalarakis,, A.G. Kalampounias, E.K. Amanatides and D.S. Mataras, (2018), Glancing angle deposition effect on structure and light-induced wettability of RF-sputtered TiO2 thin films, Micromachines, 9(8), 389.
- V.Vrakatseli, E Amanatides and D Mataras, (2016), Comparative study of RF reactive magnetron sputtering and sol-gel deposition of UV induced superhydrophilic TiOx thin films, , J. Phys.: Conf. Ser. 700 012039
- V. Vrakatseli, E. Pagonis, E. Amanatides and D. Mataras (2014), Photoinduced superhydrophilicity of amorphous TiOx-like thin films by a simple room temperature sol-gel deposition and atmospheric plasma jet treatment., J. Phys.: Conf. Ser. 550 012034
International Conferences Presentations (sample)
- E. Farsari, E.A. Kostopoulou , V. Vrakatseli, E. Amanatides and D. Mataras, Plasma enhanced chemical vapor deposition of hydrophobic, hydrophilic and amphiphilic coatings., 6th International Virtual Conference of Engineering Against Failure, 23-25 June 2021
- V. Vrakatseli, E.Farsari and D. Mataras, Fabrication of superhydrophilic and amphiphilic TiO2 thin films by glancing angle RF magnetron sputtering at low substrate temperature, , 24th International Symposium on Plasma Chemistry, 9-14 June 2019, Naples, Italy
- V. Vrakatseli, E. Amanatides and D. Mataras RF magnetron sputtering deposition of TiO2 blocking layers for perovskite solar cells, 15th International Conference on Plasma Surface Engineering 12 – 16 September, 2016, Garmisch-Partenkirchen, Germany