Molhabilidade e atividade fotocatalítica de filmes finos de TiOx depositados por magnetron sputtering em diferentes pressões parciais de O2

Abstract

Thin films of TiOx (x < 2) were deposited by triode magnetron sputtering by varying the partial pressure of O2 in the discharge (Ar + O2) to evaluate the effect of the presence of suboxides on the photocatalytic activity and the wettability of the films. For the different depositions the following partial pressures of oxygen were used, 0%, 27%, 50%, 67% and 100%. The plasma power was set at 470 W, as well the substrate temperature (400 ° C) and the total pressure (0.40 Pa). During the deposition of the films, the samples were biased with an asymmetrical bipolar pulsed source (positive reverse voltage around 10% of the negative voltage) with -200 V, frequency of 5 kHz and reverse time of 4,0 μs. X-ray diffraction measurements show that films deposited at low partial pressure of O2 (<1.3.10-2 Pa) present peaks of suboxides with different stoichiometries. The increase in partial pressure leads to a reduction in the presence of suboxides. The wettability measurements performed before and after exposure of the films to ultraviolet radiation show that the effect of photoinduced hydrophilicity is practically absent when using a methylene blue solution instead of water. The tests of photocatalytic activity show greater degradation of the solution for the samples deposited in higher partial pressures of oxygen. When the samples are irradiated during 24 h before the photocatalytic tests, there is a strong reduction in the solution degradation with the samples deposited at 0% and 27% of O2.