Temperature effect on gold nanoparticle growth and plasmonic properties.

The plasmonic properties of gold nanoparticles (NPs) have very promising prospects to enhance theefficiency in several branches of science and technology, such as in environmental, energy, biomedicaland information technology. The plasmonic properties are strongly related to the shape, size anddistribution of the NPs and to their surrounding media. Therefore, suitable techniques for optimizedNP manufacturing, as well as improved understanding of the optical characteristics of the NPs, arenecessary for progress.In this work, gold was deposited on heated substrates using DC magnetron sputtering, which is amethod with great reproducibility and suitability for large area coatings. The method is also simple touse and gives NPs at considerably lower temperatures than other heat treating manufacturingtechniques. The depositions were performed at three different substrate temperatures, and a series ofgold NP samples were manufactured at each temperature. The localized surface plasmon resonance ofthe NPs was investigated by optical measurements, and the results were related to the shape, size anddistribution of the NPs, as observed from scanning electron microscopy and image analysis. Basic physics regarding plasmonics and metal NP growth processes are also presented.The optical results show effects of particle-particle interaction, aspect ratio and size of the NPs,which are in full agreement with results on NP structure and distribution.