Optical properties of polyethylene filled with Bi$_{2}$Te$_{3}$ nanocrystallites

Composite mixtures with various component concentrations are fabricated by the thermal pressing of low-density polyethylene and Bi$_{2}$Te$_{3}$ in the powder-like state with a nanocrystal size of 50 nm. These samples preliminarily characterized by X-ray diffractometry and Raman spectroscopy are investigated by spectroscopic ellipsometry in a photon energy range of 1–6 eV. The dielectric functions for composites with a nominal Bi$_{2}$Te$_{3}$ weight concentration of 5, 10, 30, 40, 50, 60, and 70% are calculated based on the measured optical constants of polyethylene and the Bi$_{2}$Te$_{3}$ crystal in the approximation of the Bruggeman effective medium. The analysis of depolarization features of reflected light makes it possible to establish the actual inhomogeneity of the composite samples under study caused by the clusterization of nanocrystallites with an increase in the Bi$_{2}$Te$_{3}$ weight concentration in polyethylene and propose the most reliable optical model of the formed composites.