Azimuthally dependent dielectric function of SnS_0.52Se_0.48 studied by spectroscopic ellipsometry

The IV–VI alloy SnS_xSe_1-x is a layered orthorhombic semiconductor with clear in-plane optical anisotropy, important for anisotropic optoelectronic applications. In this study, we investigate the azimuth-angle-dependent dielectric function of single-crystal SnS_0.52Se_0.48 at room temperature using rotating-compensator spectroscopic ellipsometry with an angle of incidence of 64.86°. Full azimuthal rotation measurements from 0° to 360° were performed to track the evolution of the complex dielectric function between the two principal in-plane crystallographic directions. Both the real and imaginary parts of the dielectric function show strong angular dependence in spectral amplitude, while the energies of the main interband transitions remain unchanged with azimuth angle. Critical-point energies were identified by derivative line-shape analysis, confirming that the anisotropy originates from polarization-dependent optical transition strengths rather than changes in the electronic band structure. The resulting dataset provides a useful reference for crystallographic orientation determination and polarization-sensitive device design based on anisotropic SnSSe alloys.