Optoelectronic properties of sputter-deposited Ag-SiO₂ nanoparticle films by rapid thermal annealing

Silicon dioxide with embedded nano-size Ag particles has unique optical absorption due to the phenomenon known as surface plasmon resonance (SPR). SPR is the local resonance of conduction band electrons when excited by external optical fields. In this study, Ag/SiO₂ films with different Ag layers (3/5/7/10 nm) were deposited on glass sequentially by magnetron sputtering. The films then underwent the rapid thermal annealing (RTA) to create various sizes of silver particles. The RTA was carried out at elevated temperatures from 450 to 600 °C over different periods. All samples were examined by field-emission scanning electron microscope (FESEM) and surface profiler for their surface morphology. For optical properties, the films' transmittance and reflectance were measured with wavelengths ranging from 300 to 900 nm by a UV-VIS-NIR spectrophotometer. Experimental results show that for longer annealing time (15 min) and thicker deposited Ag film, larger Ag particles can be produced. These larger Ag particles on SiO₂ surface serve as the resonators of electrons to result a broader absorption under the visible light irradiation. Following the experimental results, a newly proposed fitting scheme based on the Mie solution was tested and good fits to the experimental absorbance of different films were attained.