金属纳米颗粒阵列等效薄膜的光学性质研究

Study on optical properties of equivalent film constructed by metal nanoparticle arrays

基于Maxwell—Garnett(M-G)有效介质理论,建立了研究金属纳米不连续薄膜光学性质的理论模型,对半球形纳米颗粒在等效薄膜中的体积分数和纳米尺度效应提出修正处理;给出了可见光区附近Au纳米颗粒等效薄膜的有效相对电容率和光学常数随波长变化的结果,并获得薄膜的光反射率、透射率和吸收率随膜纳米尺度的变化谱。计算结果表明,金属纳米等效薄膜有效电容率和光学常数随纳米尺度增大而增大,谱峰出现很小的红移。进一步发现,纳米尺度越小,光的反射率和吸收率越小,但透射率越大,峰值位置随纳米尺度增大有小量红移,结果与实验相符。

Based on the Maxwell-Garnett effective medium theory, a novel theoretical model for investiga- ting the optical properties of discontinuous metal nanofilm is developed,and the corrections for both the volume fraction of hemispherical nanoparticles and the nancesize effect are proposed. On the basis of the model, the variations of effective relative permittivity and optical constant of the Au nanoparticles equiva- lent film with wavelength in the visible light region are given, and the spectra of reflectivity, transmissivi- ty and absorptivity of nanofilm with nano-size effect are obtained. The computational results show that with increase of nano-size,both the effective permittivity and the optical constant increase with a slight red shift of the spectral peaks. It is further found that the, smaller the film nano-size is,the smaller the reflectivity and the absorptivity are, while the larger the transmissivity is, and there is a slight red shift of the peak positions with the nanc^size increases. These results aeree with the exnerimontn] lte