Microstructure and optical absorption property of the Cu/SiO2 nano-films

Cu/SiO2 nano-composite thin films were prepared by a sol–gel method. The structure and optical property of the films were investigated with a special emphasis on the influences of Cu content. Cu particles were basically spherical and dispersed in the SiO2 matrix. The optical absorption peaks due to the surface plasmon resonance of Cu particles were observed in the wavelength range of 550–600 nm. The absorption property is enhanced with increasing Cu content, showing a maximum value in the films with 30 at.% Cu. Increasing Cu content above 30 at.% results in a decrease in absorption intensity. The absorption peak shows a red-shift trend with increasing Cu content from 5 to 30 at.% and then turns to blue-shift by further increasing the Cu content from 30 to 35 at.%. The band gap Eg decreases with increasing Cu content from 10 to 30 at.% but increases by further increasing Cu content.