In this paper designing, preparation and characterization of multifunctional coatings based on TiO₂/SiO₂ has been described. TiO₂ was used as a high index material, whereas SiO₂ was used as a low index material. Multilayers were deposited on microscope slide substrates by microwave assisted reactive magnetron sputtering process. Multilayer design was optimized for residual reflection of about 3% in visible spectrum (450–800 nm). As a top layer, TiO₂ with a fixed thickness of 10 nm as a protective film was deposited. Based on transmittance and reflectance spectra, refractive indexes of TiO₂ and SiO₂ single layers were calculated. Ultra high vacuum atomic force microscope was used to characterize the surface properties of TiO₂/SiO₂ multilayer. Surface morphology revealed densely packed structure with grains of about 30 nm in size. Prepared samples were also investigated by nanoindentation to evaluate their protective performance against external hazards. Therefore, the hardness of the thin films was measured and it was equal to 9.34 GPa. Additionally, contact angle of prepared coatings has been measured to assess the wetting properties of the multilayer surface.

In this work results of hardness investigations of nanocrystalline TiO₂ thin films are presented. Thin films were prepared by low pressure hot target reactive sputtering (LPHTRS) and high energy reactive magnetron sputtering (HERMS). In both processes a metallic Ti target was sputtered under low pressure of oxygen working gas. After deposition by LPHTRS TiO2 thin films with anatase structure were obtained and after additional post-process annealing at 1070 K, these films recrystallized into the rutile structure. Annealing also resulted in an increase of average crystallite size from 33 nm (for anatase) to 74 nm (for rutile). The HERMS process is a modification of the LPHTRS process with the addition of an increased amplitude of unipolar voltage pulses, powering the magnetron. This effectively increases the total energy of the depositing particles at the substrate and allows dense, nanocrystalline (8.7 nm crystallites in size) TiO₂ thin film with the rutile structure to be formed directly. The hardness of the films was determined by nanoindentation. The results showed that the nanocrystalline TiO2-rutile thin film as-deposited using HERMS had high hardness (14.3 GPa), while the TiO2-anatase films as-deposited by LPHTRS, were 4-times lower (3.5 GPa). For LPHTRS films recrystallized by additional annealing, the change in thin film structure from anatase to rutile resulted in an increase of film hardness from 3.5 GPa to only 7.9 GPa. The HERMS process can therefore produce the TiO₂ rutile structure directly, with hardness that is 2 times greater than rutile films produced by LPHTRS with additional annealing step.

In this paper structural, optical, photoluminescence, and photocatalytic properties of TiO₂and TiO₂:(2.6 at. % Tb) thin films have been compared. Thin films were prepared by high-energy reactive magnetron sputtering process, which enables obtaining highly nanocrystalline rutile structure of deposited films. Crystallites sizes were 8.7 nm and 6.6 nm for TiO₂and TiO₂:Tb, respectively. Surface of prepared thin films was homogenous with small roughness of ca. 7.2 and 2.1 nm in case of TiO₂and TiO₂:Tb samples, respectively. Optical properties measurements have shown that the incorporation of Tb into TiO₂matrix has not changed significantly the thin films transparency. It also enables obtaining photoluminescence effect in wide range from 350 to 800 nm, what is unique phenomenon in case of TiO₂with rutile structure. Moreover, it has been found that the incorporation of 2.6 at. % of Tb has increased the photocatalytic activity more than two times as compared to undoped TiO₂. Additionally, for the first time in the current state of the art, the relationship between photoluminescence effect, photocatalytic activity, and surface properties of TiO₂:Tb thin films has been theoretically explained.