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.