Optical and microstructural properties of Au alloyed Al–O sputter deposited coatings

•Au-Al2O3 nanocomposites with Au contents between 0 and 11 at.% were deposited by reactive co-sputtering.•For the as-deposited coatings, the Au atoms appear to be alloyed into the amorphous oxide matrix.•Precipitation of Au nanoparticles was found in the coatings after annealing at increasing temperatures.•Surface Plasmon Resonance effect was noted only after thermal annealing at 500 °C

This research is focused on the microstructure and optical properties of an Al–O dielectric matrix incorporated with increasing Au contents up to 11 at.%. For the as-deposited coatings, the Au atoms appear to be alloyed into the amorphous oxide matrix, although a small fraction of Au atoms can also be incorporated in the form of very small nanoparticles (< 1–2 nm). Precipitation of Au nanoparticles was found in the coatings after annealing at increasing temperatures. Au clustering in the dielectric matrix was able to promote the surface plasmon resonance (SPR) effect, a desirable effect for applications in decorative and sensors fields.