Dielectric function of polycrystalline gold films: Effects of grain boundary and temperature

Abstract

The experimental data of the dielectric function of gold films are vital in metal optics since optical and optoelectronic properties depend sensitively on the dielectric function. Even though significant discrepancies of the dielectric function exist among the measurements in the past 60 years, the contribution of the grain boundary is less studied. In this work, we measured the dielectric function of three different gold films using two ellipsometers covering the spectral range from 200 nm to 25 μm. Based on the Drude model and the Mayadas-Shatzkes model of the electron-grain boundary scattering, we find that electronic reflection coefficient at the grain boundary is a vital factor to influence the dielectric function of the polycrystalline gold films. Furthermore, the temperature dependent dielectric function of gold is measured from 300 K to 800 K. Performing extended Drude analysis with a frequency dependent relaxation rate, we get a deviation of relaxation rate from the Fermi liquid theory at energies below 0.1 eV from 300 K to 800 K.

Ultrafast Thermo-Optical Dynamics of a Single Metal Nano-Object

“…The determination of ∂σ ext /∂ε 1,2 (Figure b) from optical FEM computations has been presented above. The temperature dependence of the gold dielectric function has been the object of multiple recent measurements and models. − The thermal derivatives dε 1,2 /d T extracted from these measurements strongly depend on the type of gold sample used (continuous or granular, annealed or not, deposited thickness) and on temperature. As a result, the values of the dε 1,2 /d T coefficients of gold reported in the literature are dispersed, in particular for the dε 1 /d T derivative, as ε 1 presents large values but weak relative changes with temperature in the visible range.…”

Laser-Induced Ion Formation and Electron Emission from a Nanostructured Gold Surface at Laser Fluence below the Threshold for Plasma Formation

“…At a wavelength of 355 nm, the reflectivity and the optical penetration depth are defined mainly by the imaginary part of the DF. Experimental data describing the behavior of DF at temperatures up to 770 K are given in [ 25 ] and up to 800 K in [ 26 ]. As is noted in [ 27 ], the discrepancy in the experimental data concerning the DF is associated with the sample structure and surface condition.…”

“…As is noted in [ 27 ], the discrepancy in the experimental data concerning the DF is associated with the sample structure and surface condition. Variations in the DF at a wavelength 355 nm with the temperature [ 25 , 26 ] and from sample to sample [ 26 , 27 ] do not lead to significant differences in the maximal surface temperatures calculated for both threshold values of laser fluence: from 445 to 455 K for 12 mJ/cm 2 and from 720 to 750 K for 34 mJ/cm 2 . In both cases, the maximal surface temperature is significantly below the melting point of bulk gold.…”

Design and full analysis of a metafiber-based photothermal bio-probe with perfect conversion efficiency

“…where ε ∞ = 6.7 represents the high-frequency dielectric constant [36]. The temperature-dependent plasma frequency ω p (T) and collision frequency Γ(T) are interpolated from the experimental data in [36].…”