Spectroscopic ellipsometry study of optical anisotropy inGd5Si2Ge2and comparison with reflectance difference spectra

Abstract

The complex dielectric functions of single crystals of ${\mathrm{Gd}}_{5}{\mathrm{Si}}_{2}{\mathrm{Ge}}_{2}$ were obtained using spectroscopic ellipsometry (SE) in the photon energy range of $1.5--5.0\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ at room temperature. Reflectance difference (RD) spectra for the $a\text{\penalty1000-\hskip0pt}b$ and $b\text{\penalty1000-\hskip0pt}c$ planes of single crystals of ${\mathrm{Gd}}_{5}{\mathrm{Si}}_{2}{\mathrm{Ge}}_{2}$ were derived from these dielectric functions and compared to those obtained from reflectance difference spectroscopy (RDS) at near-normal incidence. The two experimental RD spectra from SE and RDS agreed well. The in-plane optical anisotropy of the sample is mainly due to intrinsic bulk properties because of its larger magnitude $(4\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}2})$ compared to surface-induced optical anisotropies, with a magnitude of only about ${10}^{\ensuremath{-}3}$ for a typical cubic material.