Structural and Microstructural Comparison of Titania–Silica Thin Films Deposited by PE-PVD and Sol–Gel Methods as Potential Functional Coatings

Different types of materials in the TiO2-SiO2 system are widely applied in many branches of industry and science because of their valuable properties, which makes them a continuous subject of structural research. Therefore, a comparison of the structure and microstructure of TiO2-SiO2 thin films deposited using two significantly different methods, the sol–gel method and PVD with an oxygen plasma source (PE-PVD), became the main aim of this work. For particular applications, coatings obtained via the sol–gel method may exhibit selected properties comparable to those of coatings synthesized using the more demanding and expensive PE-PVD method. Additionally, bulk samples of titania and silica gels were synthesized and annealed at 500 °C, 1000 °C and 1200 °C as reference materials. XRD, GID, FTIR and Raman spectroscopy were applied as structural characterization methods. SEM and AFM were also used to investigate the surface morphology of the samples. Additional QNM AFM measurements allowed the adhesion of the samples to be determined. The hydrophilicity/hydrophobicity of the thin films was assessed using a Krüss DSA25E goniometer and ADVANCE software (version 1.11, Krüss Scientific, Hamburg, Germany), XRD, GID and FTIR measurements enabled the identification of anatase and rutile phases in the annealed gels and deposited coatings. The particle sizes were similar for all coatings, regardless of the deposition method or substrate type. Thermal cracks in the thin film obtained by dip coating strongly influenced its hydrophilicity, in contrast to the coatings obtained by PE-PVD, which exhibited hydrophobic behavior.