No abstract

Surface acoustic wave (SAW) devices with 64 μm wavelength were fabricated on a zinc oxide (ZnO) film deposited on top of an ultra-smooth nanocrystalline diamond (UNCD) layer. The smooth surface of the UNCD film allowed the growth of the ZnO film with excellent c-axis orientation and low surface roughness, suitable for SAW fabrication, and could restrain the wave from significantly dissipating into the substrate. The frequency response of the fabricated devices was characterized and a Rayleigh mode was observed at ∼65.4 MHz. This mode was utilised to demonstrate that the ZnO/UNCD SAW device can be successfully used for microfluidic applications. Streaming, pumping, and jetting using microdroplets of 0.5 and 20 μl were achieved and characterized under different powers applied to the SAW device, focusing more on the jetting behaviors induced by the ZnO SAW.

No abstract

Copper oxide films have been sputter deposited on glass substrates by reactive rf magnetron sputtering, using a solid copper target and an argon–oxygen gas atmosphere. The films were characterized by SEM/EDAX, XPS, AFM, profilometry and spectrophotometry. Optical transmission in the prepared films was measured by spectrophotometry in the 400–850 nm wavelength region. The optical transmission was found to increase from below 10% to above 80% as the rf power was reduced from 800 to 200 W at a wavelength of 550 nm. The optical bandgap value also increased from 2.05 to 2.4 eV with a reduction in rf power from 800 to 200 W. This bandgap change indicates the possibility of selectively depositing an optically transparent Cu2O-rich film, an absorbing black CuO-rich film or a mixture of both phases by varying the rf power during deposition. The oxygen flow rate during deposition had a less significant effect on the optical transmittance and bandgap of the films. This dependence of the stoichiometry of the copper oxide films on the deposition conditions is explained in terms of the sticking coefficient, nucleation rates and migration of impinging copper and oxygen species on the substrate. This information is expected to underlie the successful development of copper oxide films for technological applications requiring controlled optical transmission in the visible.

In this paper designing, preparation and characterization of multifunctional coatings based on TiO2/SiO2 has been described. TiO2 was used as a high index material, whereas SiO2 was used as a low index material. Multilayers were deposited on microscope slide substrates by microwave assisted reactive magnetron sputtering process. Multilayer design was optimized for residual reflection of about 3% in visible spectrum (450–800 nm). As a top layer, TiO2 with a fixed thickness of 10 nm as a protective film was deposited. Based on transmittance and reflectance spectra, refractive indexes of TiO2 and SiO2 single layers were calculated. Ultra high vacuum atomic force microscope was used to characterize the surface properties of TiO2/SiO2 multilayer. Surface morphology revealed densely packed structure with grains of about 30 nm in size. Prepared samples were also investigated by nanoindentation to evaluate their protective performance against external hazards. Therefore, the hardness of the thin films was measured and it was equal to 9.34 GPa. Additionally, contact angle of prepared coatings has been measured to assess the wetting properties of the multilayer surface.