Ultraviolet vacuum ultraviolet optical functions for SrTiO3 and NdGaO3 crystals determined by spectroscopic ellipsometry

Complex dielectric functions ε(E) = ε1(E) + ε2(E) were experimentally evaluated within the spectral range E = 2–25 eV and E = 2–20 eV for SrTiO3 and NdGaO3 single crystals, respectively, using synchrotron-based spectroscopic ellipsometry measurements. The ellipsometric spectra were evaluated within a framework of optical layer model taking into account sample surface roughness and anisotropy of NdGaO3. The parameters of Herzinger-Johs oscillator model were fitted to reproduce sufficiently all features of the optical spectra within the spectral range 2–10 eV. Only slight differences were revealed for spectra polarized along b and c crystallographic axes of the NdGaO3, which can confirm weak optical anisotropy.