Dependence of the far-field optical response of ion beam sculpted Cu thin films on their surface correlations

Abstract

Recent studies involving the properties of metallic nanostructures for potential technological applications are fundamentally rooted in their optical absorption and scattering properties. In this study, we report the far-field optical behavior of self organized copper (Cu) nanoripples on a glass substrate fabricated using low energy Ar+ ion beam irradiation for varying ion fluences. The optical characterization was performed by measuring the specular as well as the diffuse component in wavelength dependent transmittance spectra for the irradiated samples. Quantitative analyses has been performed on the morphology of the nanostructured films in order to extract the surface statistical parameters like roughness, wavelength, aspect ratio and correlation length. Optical responses from the nanostructured surfaces exhibit additionally strong characteristic spectra arising out of diffuse scattering as compared to the specular ones for increasing incident ion fluences. The peak intensity and sharpness observed in the transmittance spectra was found to depend largely on the surface height correlations which showed variation with increasing ion fluences. Finally, we demonstrate the dependencies of the local surface slope and the autocorrelation function in regulation of the optical transmittance of the nanoripple structured Cu thin films.