Spectroscopic ellipsometry study on the optical dielectric properties of silver platinum alloy thin films

Optical properties of alpha-phase Ag–Pt alloy films were investigated by variable angle spectroscopic ellipsometry. The silver platinum alloy films were deposited onto silicon substrates by direct current (DC) magnetron sputtering. It is observed that the dielectric functions of Ag–Pt alloy films increase with the increase of platinum concentration in the alloy. For the Ag–25 at.% Pt alloy films annealed at 300 °C, the imaginary part of dielectric permittivity is significantly decreased compared with the one before annealing. During the data simulation, the effective medium theory model was employed to characterize the surface roughness layer. X-ray diffraction (XRD) was performed to study the phase structure and grain size of the as-deposited alloy films. Two typical interband transitions around 1.9 and 3.1 eV which involve the d bands and Fermi levels were found in the silver platinum alloy films. The silver platinum alloy films may be a good material for plasmonics and metamaterials devices.

► The films of Ag–Pt alloys were deposited onto silicon substrates by DC magnetron co-sputtering.
► We studied the effect of annealing on the structure and optical properties of Ag–25 at.% Pt alloy films.
► The dielectric constants of Ag–Pt alloys with different composition were discussed systematically.
► Spectroscopic ellipsometry was used to measure the dielectric functions of Ag–Pt alloy films.
► The Ag–25 at.% Pt alloy film annealed at 300 °C is a promising material for plasmonics and metamaterials.