No abstract

Reactive High Power Impulse Magnetron Sputtering operated in multi-pulse mode (m-HiPIMS) of a pure Ti target in Ar/N 2 /O 2 gas mixture (mass flow rates of 50, 2 and 0.16 sccm, respectively) has been used for the deposition of titanium oxynitride (TiO x N y) thin films with variable content of nitrogen (from 0.6 at.% to 24.2 at.%). Increase of the nitrogen content in the deposited TiO x N y thin films determined a decrease of the optical bandgap energy and a corresponding increase of visible light adsorption. The photocatalytic activity for water molecule splitting of the films deposited on metallic substrate, which were used as the photo-anode in an electrochemical cell, has been investigated by measurements of photoelectrochemical current intensity versus biasing voltage during on/off cycles of visible light irradiation (sun light simulated by a xenon lamp). The as-deposited films have a short range order corresponding to rutile and anatase structures and showed very weak photocatalytic activity and chemical instability in the electrolyte of the photoelectrochemical cell. However, a post-deposition annealing treatment of the film with low content of nitrogen (0.6 at.%) improved considerably the visible-light photocatalytic activity, the film crystalline order and chemical stability.

No abstract

The postdischarge kinetics of reactive species produced by a surface dielectric barrier discharge (SDBD) ignited in closed-volume air for decomposition of organic molecules in aqueous solutions was investigated. A SDBD with surface of 6 cm 2 was operated in a closed volume (0.5 L) of air at atmospheric pressure. The voltage across the plasma gap, the charge transferred through the plasma, and the dissipated power were computed from the charge-voltage diagram to values of 3900V, 0.2 C, and 6W, respectively. The reactive species produced by the SDBD in a closed volume of air were active for decomposition of methylene blue molecules in small volumes of aqueous solution for a relatively long period of time af-position of organic molecules was approximately 11 minutes. However, SDBD operation in closed-volume air shortened the lifetime of polyimide dielectric of the discharge microelectrode system due to the increased humidity and reactivity of the active species generated by plasma. Measurement of relative humidity revealed that the discharge enhanced water evaporation. Atomic force microscopy investigations of dielectric surface in the discharge region roughness as the result of SDBD operation.

Titanium oxide/silicon oxide (TiO/SiO) 2D patterns were obtained by magnetron sputtering depositions of Ti on close-packed and size-reduced colloidal masks on Si and quartz substrates, followed by mask lift-off and ending with thermal oxidation. The physical processes involved in growing 2D Ti patterns and their oxidation are analyzed. For the magnetron sputtering deposition, two regimes are considered: the low-pressure regime when the flux of sputtered atoms is anisotropic, and the high-pressure regime, when the flux of sputtered atoms is isotropic due to frequent collisions. Moreover, magnetron sputtering operation modes, such as dc sputtering and high power impulse sputtering, are compared. The changes in pattern size and morphology determined by the oxidation of the Ti patterns and Si substrate are analyzed. The hydrophilicity induced by UV-light irradiation and the visible-light photocatalytic activity towards the degradation of the methylene blue of the fabricated TiO/SiO patterns were considerably higher when compared to the performances of uniform TiO films.