Formation and Modeling of Nanosized Levels of the Self-organized Structures in the Non-crystalline Thin Films of Ge-As-Te(S, Se) Systems

A model of thermal instability and the formation of self-organized structures under the action of continuous infrared radiation of a CO2-laser on amorphous condensates of Ge-As-Te (S, Se) systems applied to quartz or mica substrates is proposed, and its analysis is based on experimental studies. It is shown that the uniform distribution of the temperature field along the beam section at the power density of the radiation P > Pc (Pc = 1.8-8.5 W/cm2) becomes unstable and a radial-ring structure with a spatially inhomogeneous profile of the temperature field is formed. It is established that the bifurcation of thermal instability and the formation of a non-uniform temperature profile are carried out at the expense of self-regulating mechanisms, which lead to saturation of the absorption nonlinearity and equalization of the growth rate of the absorbed energy by heat transfer into the amorphous layer. Dependence of the threshold density of the infrared radiation power of the formation of ordered radial-ring structures on the irradiation duration is investigated. A bifurcation diagram in a plane {radiation power (P), temperature (T)} that describes the singular behaviour of optical density depending on the duration of exposure to radiation is constructed. It is shown that a radial-ring structure with the number of rays m ≥ 3 is formed for amorphous condensates of Ge-As-Te (S, Se) systems at irradiation power densities P ≥ 18.6 W/cm2, which is consistent with the experimental data. The peculiarities of the behaviour of self-organized structures in thin-film layers are analyzed, namely the sensitivity of the system to the technological conditions of obtaining, the parameters of electromagnetic radiation and the possibility of realization of the butterfly effect. The ways of formation and implementation of fractality by nanosized levels of structuring and lifetime for the self-organized structures in the presented non-crystalline materials of Ge-As-Te (S, Se) systems are considered.