Sol-gel preparation of Ag/SiO2 nano-composite films and their optical absorption properties

The Ag/SiO2 composite thin films with 50wt% Ag were prepared on a glass substrate by a sol-gel method at different annealing temperatures for 0.5 hour. The phase structure was characterized by XRD and optical absorption spectra were measured in the range of 200 similar to 1000 nm by a ultraviolet spectrometer. The preparation process of composite thin films and effects of different heat treat temperatures on optical absorption properties were investigated. The DSC result shows that Ag particles were formed at 200 degrees C and the remnant organic compound was completely decomposed at 300 degrees C. The mean diameter of the Ag particles in the films is about 20 nm after annealing at 500 degrees C. The optical absorption peaks due to the surface plasmon resonance appear in the wavelength range of 420438 nm. With the annealing temperatures increasing the intensity of the absorption peaks increase and the blue shift of SPR peaks occurs.