In this work, thin films based on the Ti-Zr system were studied, deposited on a silicon substrate by the magnetron sputtering technique using simultaneously a combination of High-Power Impulse Magnetron Sputtering (HiPIMS) and Direct Current Magnetron Sputtering (DCMS) sources. The objective of this work is analyzing the effect of varying HiPIMS frequency (300 Hz, 400 Hz, 500 Hz, and 600 Hz) on the characteristics and properties of the thin films. The thickness increased between 300 Hz and 500 Hz, where the thickness measured 563 nm and 732 nm, respectively; then it decreased to 709 nm at 600 Hz. Hardness and elastic moduli also tended to decrease with increasing frequency, and the results for the first property were between 7 GPa and 10.3 Gpa, while the elastic moduli were from 114 Gpa to 157 Gpa, in which lower values were reached at higher frequencies. In the wettability test, lower contact angles were observed for samples with lower frequencies due to their high surface energy, providing better hydrophilic properties.

The present paper sets out to investigate the role of voltage pulse length on the properties of Nb:TiO2 films deposited by High Power Impulse Magnetron Sputtering (HiPIMS). Several characteristics of the films were investigated, namely, resistivity, transmittance, crystallinity and band gap values of Nb:TiO2 films. Reactive depositions were carried out in Ar/O2 plasma with 40 µs, 50 µs, 60 µs, and 70 µs pulses. Increasing the pulse length changes the deposition from compound to metal mode. As it gets closer to metal mode, the deposition rate increases by up to one order of magnitude, while the resistivity of the resulting Nb:TiO2 film becomes as low as 10-4 Ω.cm, without any significant loss in optical transmittance, which remains close to 90% for a wavelength around 450 nm, but reduction in 25% of heat transmission (above 800 nm) were observed. Results indicate the anatase phase for all deposition conditions, and Ti3+ states increase with the pulse length, which can be explained by the generation of a second band gap. Both the niobium doping and the Ti3+ states can contribute to increase the conductivity of the Nb:TiO2 films in the as-deposited condition.

Resumo Filmes de TiO2 dopados com Nb podem associar propriedades como TCO (transparent conductive oxide) e super-hidrofilicidade, quando ativados por luz UV. Filmes metálicos de Ti-Nb foram depositados sobre substrato de vidro via triodo magnétron sputtering e posteriormente os filmes foram oxidados em atmosfera ambiente a 600 °C durante 1,0 h em condições similares àquelas usadas no tratamento térmico de vidros. Medidas de rugosidade, cristalização, composição química e molhabilidade foram realizadas através das técnicas de microscopia de força atômica, difração de raios X, fluorescência de raios X e ângulo de contato, respectivamente. Os resultados mostraram que os filmes foram completamente oxidados, tornando-se visualmente transparentes à luz visível com cristalização da fase rutilo-TiO2. Após irradiação com luz UV, os filmes TiO2:Nb apresentaram rugosidade em escala nanométrica podendo ser classificados como super-hidrofílicos, com valores de ângulo de contato similares àqueles de filmes de TiO2 puros, preservando características de filmes autolimpantes.

Abstract Niobium doped TiO2 films can combine properties of TCO (transparent conductive oxide) with superhydrophilicity activated by UV radiation. Ti-Nb metal films were deposited on a glass substrate through triode magnetron sputtering. Afterward, the Ti-Nb metallic films were oxidized at 600 °C during 1.0 h in air atmosphere, with similar parameters of those used in glass heat-treatment. Measurements of roughness, crystallization, chemical composition, and wettability were carried out through atomic force microscopy, X-ray diffraction, X-ray fluorescence, and contact angle, respectively. Results showed that all films were crystallized as rutile-TiO2 phase and were transparent in visible range. TiO2:Nb films showed nanometer roughness that can be classified as superhydrophilic, after activation with UV light. The contact angle values were similar to those of pure TiO2 films, that is, the TiO2:Nb films preserved the self-cleaning properties.