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TiO2 thin films were deposited by dc magnetron sputtering from sub-stoichiometric TiO2−x targets. The as deposited films were XRD amorphous and their microstructure was varied by changing the Ar-pressure and the applied dc power during sputtering. An anneal treatment at 673 K/1 h in air resulted in the crystallization of a preferentially oriented anatase phase, the degree of which depended on the deposition conditions. The microstructure, optical and photocatalytic properties of the thin films were investigated using SEM, UV–VIS spectroscopy and a custom made photocatalytic test reactor, respectively. The thin film density was estimated from their refractive index. Density and crystallinity were the most important factors determining the photocatalytic activity of the thin films.

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TiO 2 thin films of 200 -300 nm thickness were deposited by d.c. magnetron sputtering onto glass substrates from a semiconducting TiO 2Àx target in pure Ar using pressures between 0.1 and 1.0 Pa. The obtained TiO 2 coatings are transparent and have refractive indices between 2.5 and 1.9. Post deposition heat treatment at different temperatures was performed to achieve crystallization of anatase TiO 2 . The as-deposited and heat treated films were examined with UV -VIS (transmission), SEM and XRD to investigate the influence of the argon pressure during deposition on the structural development during heat treatment. Additionally, the photocatalytic activity of the films was tested by measuring the decomposition rate of ethanol in a controlled gas atmosphere simulating air, and was related to their respective microstructures. D

In sputter magnetrons the electrons emitted from the target, the so-called secondary electrons (SE), can be recaptured by the target. As a result, not all emitted SE will interact with the discharge gas. The effective gas interaction probability (EGIP) is the probability that an emitted SE interacts with the discharge gas, and thus is not recaptured by the target. To calculate the EGIP an analytical model is developed. The model is verified by comparing its results with those of a Monte Carlo model.The EGIP of an individual SE is strongly, and in a complex manner, dependent on the electric and magnetic field to which the electron is subjected and on its initial starting conditions. Therefore, it is useful to introduce the average EGIP of the discharge which is a weighted average of the individual EGIP values. The influence on the EGIP of different parameters, such as the initial energy of the SE, the electron reflection coefficient and the electric and magnetic field is discussed. For typical discharge conditions at a pressure of 0.5 Pa values for the average EGIP in the range of 0.25–0.35 are found. This means that the recapture probability lies typically between 65% and 75%, showing that it is necessary to take into account this process to accurately model and simulate the magnetron discharge.