2 May 2014 Permittivity, specific resistivity and surface roughness of silver nanolayers for plasmonic applications
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Abstract
We report on measurements of optical, morphological and electrical properties of silver nanolayers. The Ag films of thickness from 10 to 500 nm are deposited in e-beam evaporator. Fused silica and sapphire substrates are used with nominal root-mean-square (RMS) roughness equal 0.3 and 0.2 nm, respectively. Silver is deposited either directly on substrates or on Ge, Ni, or Ti wetting interlayer. The refractive index n and the extinction coefficient κ of Ag films are derived from spectroscopic ellipsometry and reflectance measurements carried in air in the spectral range from 0.6 to 6.5 eV (2200 – 193 nm) using a rotating analyzer ellipsometer (V-VASE, J.A. Woollam Co.). Surface roughness is measured using AFM (Ntegra NT-MDT) under tapping mode in air with sharp etalon probes and 5:1 aspect ratio. Ag layers of 10 and 30 nm thickness have nearly the same RMS roughness when deposited at temperatures from 180 to 350 K. The lowest RMS=0.2 nm is achieved for 10 nm film Ag/Ge evaporated at 295 K. The sheet resistance of the Ag films is measured using two methods: the van der Pauw method with the electrical contacts located on perimeters of the samples and four probes contacting the samples at points lying in a straight line. Specific resistivity of Ag films on fused silica change from <109 to 1.80 [μΩ∙cm] when thickness increases from 10 to 500 nm. Specific resistivity of 10, 30 and 50 nm thick Ag films on 1 nm Ge wetting layer are equal 14.01, 7.89, and 5.58 [μΩ∙cm], respectively, and are about twice higher than those of Ag films on Ti or Ni interlayers.
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T. Stefaniuk, P. Wróbel, A. A. Wronkowska, A. Wronkowski, P. Trautman, T. Szoplik, "Permittivity, specific resistivity and surface roughness of silver nanolayers for plasmonic applications", Proc. SPIE 9125, Metamaterials IX, 912519 (2 May 2014); doi: 10.1117/12.2058593; https://doi.org/10.1117/12.2058593
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