Influence of the surface roughness on the properties of Au films measured by surface plasmon resonance and X-ray reflectometry

• Published in: Thin solid films 2011-01, Vol.519 (7), p.2093-2097
• Main Authors: Velinov, Tzvetan, Ahtapodov, Lyubomir, Nelson, Andrew, Gateshki, Milen, Bivolarska, Maria
• Format: Article
• Language: English
• Subjects: Chromium; Collective excitations (including excitons, polarons, plasmons and other charge-density excitations); Condensed matter: electronic structure, electrical, magnetic, and optical properties; Electronic structure and electrical properties of surfaces, interfaces, thin films and low-dimensional structures; Evaporation; Exact sciences and technology; Glass; Gold; Mathematical models; Optical properties; Optical properties and condensed-matter spectroscopy and other interactions of matter with particles and radiation; Optical properties of specific thin films; Physics; Plasmons; Roughness; Surface and interface electron states; Surface plasmon resonance; Surface roughness; Thin films; X-ray reflectometry; X-rays
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2010.10.059

Thickness and refractive index of Au films thermally evaporated onto glass substrates and with an underlayer of Cr are determined from surface plasmon resonance. The results for the thickness are found to agree very well with those from X-ray reflectivity when a simple model of layers with flat interfaces is used. Plasmon propagation along thin films is influenced by radiative damping due to scattering from surface roughness. To study this influence the surface roughness of the glass substrate, Cr an Au layers are measured by X-ray reflectometry and the results used to introduce three intermediate layers with effective refractive indices and thicknesses corresponding to the roughness. Then Fresnel's equations are used to fit the reflectivity and to deduce the layer properties. It is found that the roughness affects to a great extent the optical parameters of the Au films even when it is smaller than 1 nm. In particular, the absolute value of real part of the dielectric constant decreases while its imaginary part increases when those effects are not taken into account.