Influence of Ambient Atmosphere on the Plasmon Resonance Absorption of Ag/SiO_x (0 ≤ x ≤ 2) Nanocomposite Film

Nanocomposite films consisting of nanosized Ag particles embedded in partially oxidized amorphous Si-containing matrices were prepared by the radio frequency magnetron co-sputtering deposition. We studied the influence of ambient atmosphere during the preparation and heat-treatment of Ag/SiO_x (0 ≤ x ≤ 2) nanocomposite film on its optical absorption properties. We found that the plasmon resonance absorption peak shifts to shorter wavelengths with theincreasing oxygen content in the SiO_x matrix. The analysis indicates that the potential barrier between Ag nanoparticles and SiO_x matrix increases with the increasing x value, which will induce the surface resonance state to shift to higher energy. The electrons in the vicinity of the Fermi level of Ag nanoparticles must absorb more energy to be transferred to the surface resonance state with the increasing x value. It was also found that the plasmon resonance absorption peaks of the samples annealed in different ambient atmospheres are located at about the same position. This is because the oxidation surface layer is dense enough to prevent the oxygen from penetrating into the sample to oxidize the silicon in the inner layer.