Special Section on Advances in Nanostructured Thin Films

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

[+] Author Affiliations
Ming-Ying Zhang, Zi-Yi Wang, Rong-Jun Zhang, Yu-Xiang Zheng, Song-You Wang, Liang-Yao Chen

Fudan University, Department of Optical Science and Engineering, 220 Handan Road, Shanghai 200433, China

Tian-Ning Zhang, Yun Zhang, Xin Chen, Yan Sun

Chinese Academy of Sciences, Shanghai Institute of Technical Physics, National Laboratory of Infrared Physics, 500 Yutian Road, Shanghai 200083, China

J. Nanophoton. 10(3), 033009 (May 12, 2016). doi:10.1117/1.JNP.10.033009
History: Received December 15, 2015; Accepted April 22, 2016
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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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© 2016 Society of Photo-Optical Instrumentation Engineers

Citation

Ming-Ying Zhang ; Zi-Yi Wang ; Tian-Ning Zhang ; Yun Zhang ; Rong-Jun Zhang, et al.
"Thickness-dependent free-electron relaxation time of Au thin films in near-infrared region", J. Nanophoton. 10(3), 033009 (May 12, 2016). ; http://dx.doi.org/10.1117/1.JNP.10.033009


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