Optical Properties of Polyethylene Filled with Bi2Te3 Nanocrystallites

Resumo

Composite mixtures with various component concentrations are fabricated by the thermal pressing of low-density polyethylene and Bi₂Te₃ 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 Bi₂Te₃ weight concentration of 5, 10, 30, 40, 50, 60, and 70% are calculated based on the measured optical constants of polyethylene and the Bi₂Te₃ 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 Bi₂Te₃ weight concentration in polyethylene and propose the most reliable optical model of the formed composites.