The influence of hydrogen addition to an Ar plasma on the structural properties of TiO2−x films produced by RF sputtering of a TiO2 target at room temperature was studied. The structural properties of the films were characterized by x-ray photoelectron spectroscopy while the surface morphology was analysed using scanning electron microscopy (SEM). The valence band analysis showed the crystal field splitting of d states into doubly and triply degenerate states. H2 addition to the Ar plasma created additional d-state splitting due to distortions in the TiO2 structure by the Jahn–Teller mechanism. The occurrence of the Jahn–Teller split is well-correlated with oxygen vacancies in the TiO2−x films. Water adsorption at the TiO2−x surface and film hydroxylation were also addressed. The as-grown films were amorphous and SEM analysis showed a columnar structure for all the films but with a lower packing density of the columns after H2 introduction in the Ar plasma.

In this work, TiO2 films produced by rf sputtering of a TiO2 target in argon and argon–oxygen plasmas were studied. The oxygen content in the feed gas was varied in a range 3–20%. The chemical composition and structure of films were characterized by Rutherford backscattering spectrometry, x-ray photoelectron spectroscopy (XPS) and x-ray diffraction. Important information about the intrinsic defects of the films and their effects on the optical properties as well as a scheme of the energy band structure of the films could be derived from a combined use of optical spectroscopy and XPS.

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In this work the effect of air plasmas on wettability of Polydimethylsiloxane (PDMS) and polyethylene terephthalate (PET) was studied. These polymers are widely used materials in the fabrication of microfluidic devices. The microfluidic system fabricated from native PET and PDMS requires active pumping mechanism, due to a low hydrophilic surface behavior. To render hydrophilic and increase the capillary flow into the device, plasma treatments can be used. Air plasma treatment is an interesting technology for microfluidic fields due to simplicity of use and low cost. This study describes the effect of the working plasma pressure on wettability of polymers. The polymers were treated by RF plasma and the wettability was studied by means of sessile contact angle. The results established that the air plasma can increase the wettability of both polymers. Moreover we demonstrated that by optimizing the working pressure a superhydrophilic surface (with a contact angle less than 5°) can be obtained. The findings suggest that air plasma treatments are a suitable technology to enhance polymers surface wetting performance for microfluidic devices.

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