Petretskyi S. Low-temperature thermal conductivity of wide-bandgap chalcogenide glasses at changing the local coordination and characterization of films with a high connectivity for ray optics

The thesis is devoted to the study of the concentration (coordination) features of the thermal dependence of thermal conductivity k(T) in wide-bandgap chalcogenide glasses at a temperature interval of 2.5 to 100 K, for finding the compositions with a high thermal conductivity and a connected structural matrix- for ray optics. It was established that the increasing of the average coordination number z = 3y + 2(100-y) the thermal conductivity level in AsyS100-y glasses increases and at a fixed temperature is accompanied by a shift of the Boson peak to a high-frequency region of the spectrum from 19 cm-1 (z = 2.1) to 26 cm-1 (z = 2.4), lowering the intensity of the low-frequency maximum, increasing of the ultrasound velocity, and agrees with the position of the topological-cluster (TC) concept of increasing the connectivity of the glass structure due to an increase in inter-chain interaction and cross-linking of one-dimensional clusters in a layered chain at approximation to As40S60 composition, z = 2.4, (transition 1D-2D). The comparison of the distribution of elements were performed and the film surfaces were characterized for ray optics applications during the transition from As2S3-GeS2-Ge2S3.