Microstructure and strong optical absorption property of the Ag/Al2O3 nano-films

• Ag nanoparticles dispersed Al2O3 composite films were prepared by a sol–gel method.
• Spherical Ag particles have average diameters in the range from 3 nm to 12 nm.
• Absorption was enhanced by increasing Ag contents at relatively low concentration.
• Relatively high Ag contents result in a decrease in optical absorption intensity.

Ag/Al2O3 nano-composite thin films were fabricated by a sol–gel method, and the nanostructure and optical property of the films were investigated. Ag particles with average diameters of 3–12 nm were formed about 500 °C, and dispersed in the Al2O3 matrix. The optical absorption peaks due to the surface plasmon resonance of Ag particles were observed in the wavelength range of 410–430 nm. The optical absorption is intensified with increasing Ag content, showing a optimal value in the films with 40 mol% Ag. The absorption spectra of Ag/Al2O3 thin films with 10 mol% to 40 mol% Ag are in good accordance with the theoretical optical absorption spectra. Increasing Ag content over 40 mol% results in the partial connection of Ag particles, and hence the intensity of the absorption peak is weakened. The resonance peaks of the Ag/Al2O3 films show a red-shift trend with the increase of Ag content.

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