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Au/Al2O3 nanocomposite films, studied in this work, were prepared by RF-magnetron sputtering technique on glass substrate at room temperature under two different argon pressures, and subsequent heat treatment. Formation of gold nanoparticles was confirmed by X-ray diffraction patterns and UVvisible absorption spectroscopy. Au fill fraction f, changed from f=10.78% to f=25.45%, when argon pressure increased from 2x10-3 mbar to 10x10-3 mbar. For the as-deposited samples, reduction in volume fraction of gold particles causes a decrease in particle size, a lattice expansion and a blue-shift of the SPR peak position. An opposite trend is observed in the lattice parameter with respect to the gold volume fraction for the annealed samples. A small change in the sizes is observed and no significant shift of band absorption peak in samples of low Au content. However, at higher Au concentration, an appreciable red shift of the surface plasmon resonance with increasing temperature is observed. Experimental optical absorption spectra of all the samples were theoretically simulated by Maxwell-Garnett effective medium theory.

No abstract

Au/SiO 2 nanocomposite films, studied in this work, were prepared by RF-magnetron sputtering technique on glass substrate at room temperature under two different substrate temperatures (Ts), and subsequent heat treatment. For the deposited sample at T S = 25˚C, no apparent surface plasmon resonance peak could be observed. After annealing, optical absorption spectrum of the Au/SiO 2 thin films showed a broad absorption band around 500 nm relating to gold nanoparticles without any modification in the position of the SPR and the size of particles. For the series deposited at T S = 400˚C, the surface plasmon resonance (SPR) was found at 500 nm. After heat treatment it's redshift from 500 nm to 503 nm, while the size increases from 2.01 nm to 2.3 nm. We have also shown that, as the AuNPs are embedded in silica films, the small nanoparticles size have a slightly larger expansion coefficient than for bigger one.