Local modification of the microstructure and electrical properties of multifunctional Au-YSZ nanocomposite thin films by laser interference patterning.

Nanocomposite films consisting of gold nanoparticles embedded in an yttria-stabilized zirconia matrix (Au-YSZ) have been synthesized with different gold loadings by reactive magnetron sputtering followed by ex situ annealing in air or laser interference patterning (LIP) treatment. It is shown that the electrical conductivity of the nanocomposite films can be modified to a large extent by changing the gold loading, by thermal annealing, or by LIP. The structural and microstructural analyses evidenced the segregation of metallic gold in crystalline form for all synthesis conditions and treatments applied. Thermal annealing above 400 °C is observed to trigger the growth of pre-existing nanoparticles in the volume of the films. Moreover, pronounced segregation of gold to the film surface is observed for Au/(Au + Zr + Y) ratios above 0.40, which may prevent the use of thermal annealing to functionalize gold-rich Au-YSZ coatings. In contrast, significant modifications of the microstructure were detected within the interference spot (spot size close to 2 × 2 mm) of LIP treatments only for the regions corresponding to constructive interference. As a consequence, besides its already demonstrated ability to modify the friction behavior of Au-YSZ films, the LIP treatment enables local tailoring of their electrical resistivity. The combination of these characteristics can be of great interest for sliding electrical contacts.

Using STED and ELSM confocal microscopy for a better knowledge of fused silica polished glass interface.

Characteristics and nature of close surface defects existing in fused silica polished optical surfaces were explored. Samples were deliberately scratched using a modified polishing process in presence of different fluorescent dyes. Various techniques including Epi-fluorescence Laser Scanning Mode (ELSM) or STimulated Emission Depletion (STED) confocal microscopy were used to measure and quantify scratches that are sometimes embedded under the polished layer. We show using a non-destructive technique that depth of the modified region extends far below the surface. Moreover cracks of 120 nm width can be present ten micrometers below the surface.