Electronic structure and plasmonic activity in co-evaporated Ag-In bimetallic alloys

Abstract

Thin Ag-In films, covering the whole range of compositions from 0 to 100 at% In, were deposited by thermal co-evaporation. Alloying and formation of solid solutions and intermediate phases were realized without further processing of the films. The phase composition was analyzed by X-ray diffraction. The spectra of the complex permittivity, ε were determined by spectroscopic ellipsometry and their compositional dependencies were traced out in terms of their electronic structure, calculated using the Density-functional theory (DFT). The analysis of the Lorentz component of the spectra of the complex permittivity showed that the increase of the indium content in the thin layers leads to a decrease in the number of electrons participating in the interband transitions with energies of 4–6 eV, which causes improvement of their plasmon activity in the ultraviolet spectral range. It was found out that the thin films containing intermediate Ag-In compounds in their structure are the most perspective for excitation of plasmon resonance in this spectral region of interest.