Ellipsometric study of interband transitions in orthorhombic GeS

Abstract
Ellipsometric measurements have been used to determine the principal components of the dielectric tensor of orthorhombic crystalline GeS between 1.66 and 5.5 eV. Measurements have been taken from the cleavage plane and a second plane perpendicular to it. Calculations of the dielectric tensor have been done, using measurements at a large number of angles of incidence from the two surfaces. Critical-point energies for the light vector E→ parallel to the a→,b→,c→ directions and their broadening parameters were obtained by an analysis of the second-derivative spectra. The critical-point energies show only weak dependence on polarization.