Bendak A. Deposition, Structure and Physical Properties of Thin Films Based on Cu6PS5X (X= I, Br), Cu6PSe5I and Cu7GeS5I Argyrodites

The thesis is devoted to the preparation of thin films on the basis of Cu6PS5X (X= I, Br), Cu6PSe5I and Cu7GeS5I superionic compounds with the argyrodite structure, the study of the relationship between their structural, electrical, mechanical, and optical properties, as well as the influence of external factors on these properties. Thin films were obtained on the base of compounds with the argyrodite structure using the method of magnetron sputtering and HiTUS technology. It was found that with increasing copper content in Cu6PS5I-based thin films their electrical conductivity nonlinearly increases, hardness, energy pseudogap, and the Urbach energy nonlinearly decrease and the refractive index nonlinearly increases. The decrease of the Urbach energy indicates the processes of the structure ordering that occurs at the copper content increase in the Cu6PS5I-based films. In comparison with crystalline argyrodites, in the thin films on their basis, a decrease of the electrical conductivity and the energy pseudogap is observed as well as an increase of the electron-phonon interaction, an increase of the refractive index and the Urbach energy, and, consequently, the increasing structural disordering. The observed considerable broadening of bands in the Raman scattering spectra of Cu6PS5I-based thin films compared to those of the single crystals is the evidence for the amorphous structure of the films where due to the short-range order the PS4 structural groups are preserved, although their structure is noticeably distorted. With increasing duration of X-ray and electron irradiation of argyrodite-based thin films, a decrease in the energy pseudogap, as well as an increase in Urbach energy and the refractive index, was revealed. The increase in the Urbach energy due to the absorption edge smearing is the evidence for increasing structural disordering under the X-ray and electron irradiation.