Thickness-dependent free-electron relaxation time of Au thin films in near-infrared region

Ming-Ying Zhang; Zi-Yi Wang; Tian-Ning Zhang; Yun Zhang; Rong-Jun Zhang; Xin Chen; Yan Sun; Yu-Xiang Zheng; Song-You Wang; Liang-Yao Chen

doi:10.1117/1.JNP.10.033009

12 May 2016 Thickness-dependent free-electron relaxation time of Au thin films in near-infrared region

Ming-Ying Zhang, Zi-Yi Wang, Tian-Ning Zhang, Yun Zhang, Rong-Jun Zhang, Xin Chen, Yan Sun, Yu-Xiang Zheng, Song-You Wang, Liang-Yao Chen

Author Affiliations +

Funded by: National Natural Science Foundation of China, National Science Technology Major Project of China

Journal of Nanophotonics, Vol. 10, Issue 3, 033009 (May 2016). https://doi.org/10.1117/1.JNP.10.033009

Abstract

The free-electron relaxation time is a crucial property to be considered in the design of optical devices, because it determines the dielectric function. Thus, an accurate understanding of this relaxation time is essential for design optimization. Some simulations showed that the relaxation times of Au thin films with thicknesses below 30 nm are different from those of the bulk material. Therefore, we deposited films with four different thicknesses below this value and used near-infrared spectroscopic ellipsometry to show that the relaxation time is dependent on the film thickness. We fitted the ellipsometry spectrum of Au thin films with a thickness <30 nm and found the imaginary part of the dielectric function of the thin films to vary with the film thickness in the near-infrared region. Furthermore, different relaxation times were used to simulate the reflectance of a Fabry–Pérot absorber and a plasmonic metamaterial absorber. The simulation results indicated that the obtained relaxation time enables a more reliable evaluation of optical device design.

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Ming-Ying Zhang, Zi-Yi Wang, Tian-Ning Zhang, Yun Zhang, Rong-Jun Zhang, Xin Chen, Yan Sun, Yu-Xiang Zheng, Song-You Wang, and Liang-Yao Chen "Thickness-dependent free-electron relaxation time of Au thin films in near-infrared region," Journal of Nanophotonics 10(3), 033009 (12 May 2016). https://doi.org/10.1117/1.JNP.10.033009

Published: 12 May 2016

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