The optical absorption properties of Ag nanoparticles embedded in partially oxidized amorphous silicon matrices

Nanocomposite films consisting of nanosized Ag particles embedded in partially oxidized amorphous Si matrices were prepared by the radio frequency magnetron co-sputtering method. Effects of the subsequent heat treatments at different temperatures ranging from 200 degreesC to 500 degreesC on the optical absorption properties of the films were investigated by spectrometry. The analysis shows that the blue shift of the plasmon resonance absorption peak position of Ag nanoparticles does not originate from the different oxidation degrees of Si matrices. A deviation from the (1/R) dependence of peak width on the particle size is probably due to the activity of the interface of the Ag nanoparticles and the Si matrix. The concept of a "Surface resonance state" is introduced to discuss the blue shift of the peak position, the decrease of the peak intensity and the broadening of the peak width with decreasing size of the Ag particles together with "quantum size effect".