Effect of chemical ordering on optical properties of Fe3Si epitaxial films

Optical characteristics (electron energy loss function, optical conductivity sigma, permittivity epsilon, refractive index n, extinction coefficient k, and absorption coefficient alpha) of a 30 nm thick epitaxial Fe3Si iron silicide films grown at different silicon substrate temperature (26, 100, 200, 300 degrees C) were determined within E = 0.74-6.46 eV photon energy range using spectroscopic ellipsometry technique. The experimental data are compared to the optical characteristics calculated in the framework of the density functional theory using the GGA-PBE approximation. Variations of the optical characteristics spectra are discussed from the point of view of chemical ordering of DO3 type crystal structure. It is asserted that the electron energy-loss function, optical conductivity and extinction coefficient of the Fe3Si iron silicide films undergo noticeable changes in different spectral ranges over the whole spectrum between 0.74 and 6.46 eV due to variation in the chemical order. Information on the effect of chemical ordering on the optical properties obtained here allows one to carry out quick qualitative analysis of Fe3Si film crystal quality during the synthesis procedures by ellipsometry method in situ.