Structural and optical characterization of thin films from bimetallic Au-Sb system as tuneable plasmonic material for UV spectral range

Abstract

The optical properties of silver and gold based bimetallic alloys make possible to adjust their plasma frequency. The direct alloying and plasmonic activity of thin layers from the Au-Sb system are presented in the present work. The thin films were deposited by thermal co-evaporation of gold and antinomy. The chemical and phase composition of thin films, were analysed by X-ray microanalysis and X-ray diffraction (XRD), respectively. The results of the X-ray microanalysis show that the composition of the thin layers corresponds well to the predetermined. The XRD patterns, depending on the envisaged compositions, show formation of intermetallic compound AuSb2 and binary alloys between the initial elements and the intermediate compound, which is in accordance with the Au-Sb phase diagram. The dispersion of the complex permittivity was determined by spectroscopic ellipsometry. The results show that the increase of the antimony content leads to an increase of the values of the imaginary part of the complex permittivity in the visible spectral region at photon energies greater than 3 eV, and a decrease in the ultraviolet spectral region. Based on the obtained dispersions of the complex permittivity, extinction cross-sections and local field enhancement of spherical Au-Sb nanoparticles were determined and their plasmon activity was evaluated.