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Active research of the GeSbTe material (GST225) is connected with the possibility of creating multi-level non-volatile elements for high-speed integrated optical functional circuits. The principle of multi-level recording in these devices is based on the formation of regions in GeSbTe thin films with partial crystallization and significantly different optical properties. To predict the parameters of the effect that initiates phase transformations and reliably ensure a reversible transition between a set of logical states, it is necessary to have reliable information about the optical characteristics of GeSbTe thin films in states with different degrees of crystallization and the conditions for their production. Thereby, the purpose of this research was to determine the influence of phase state GeSbTe films on the extinction coefficient ( k ) and refractive index ( n ) and study changes in the values of optical band gap depending on the annealing temperature have been considered. The obtained samples of GeSbTe thin films were examined using atomic force microscopy, X-ray phase analysis, and energy dispersion X-ray phase analysis, and energy-dispersive microanalysis to determine the film thickness, morphology, phase state, and composition of the films. The ellipsometry method was used to obtain the spectra of ellipsometric angles ψ and Δ (the amplitude and phase components of light wave) and the parameters n and k were determined. The influence of layer and mathematical models on the calculation dispersion of optical parameters of GeSbTe films, have been considered. It was found a significant increase in the values of n and k on the wavelength of 1550 nm when annealing above 200 °C has been found. It has been shown that in the amorphous state, GeSbTe thin films have an optical band gap equal to 0,71 eV, and in the crystalline = 0,47 eV. It was determined that the dependences of the refractive index, extinction coefficient, and optical band gap on the degree of crystallization of GeSbTe thin films are close to linear.

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The centrifuging method is advantageous in manufacture, for instance, of films with large area and/or of large thickness of several microns, but for chalcogenide compounds it is not commonly used yet, because they have relatively weak solubility in most solvents. Therefore, the search for the optimal conditions of preparing the solutions of chalcogenide compounds and manufacturing films by the centrifuging method currently is an urgent problem. The features of the amorphous arsenic sulfide (AsS) films prepared by the method of centrifuging the solution in n-butylamine have been investigated. The synthesized films have been characterized using the X-ray diffraction, IR spectroscopy, atomic force microscopy (AFM) and the Raman scattering. It has been shown that the amorphous films AsS are characterized by an increased index of the elasticity modulus compared to the films of an analogous composition, prepared by the film thermal deposition and by AsS glass. To explain the obtained experimental results, a structural model, built on the basis of arsenic sulfide clusters, the surfaces of which are limited by the negatively and positively charged ions, has been used. Direct conductivity (d.c.) studies have shown that the amorphous films exhibit a semiconductor conductivity character, while they have conductivity at room temperature of ~10 S/cm, which indicates to good dielectric properties. The prepared films have an optical transparency beginning from the yellow wavelength range, which makes them promising functional materials for technical applications in optics and photonics.

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