CHANGES IN THE STRUCTURE OF NANOSIZED AMORPHOUS GE2SB2TE5<BI> FILMS UNDER LASER IRRADIATION

Abstract

In this paper, the results of studies of changes in the structure of bismuth-modified nanosized amorphous films of composition Ge₂Sb₂Te₅ (Ge₂Sb₂Te₅<Bi>) under laser irradiation. Modified by the ~90 nm thickness method obtained by ion-plasma magnetron RF co-sputtering of a polycrystalline target of Ge₂Sb₂Te₅ and bismuth in an argon atmosphere. The composition of the films and the amorphism of their structure were controlled by energy dispersive analysis (EDX) on a SEM Quanta 3D 200i and transmission electron microscopy. The bismuth impurity concentration in the films varied from 2.6 to 16.5 at.%. Changes in a small number of amorphous films under the action of laser irradiation were recorded in situ by Raman spectroscopy. It is shown that in nanosized Ge₂Sb₂Te₅ and Ge₂Sb₂Te₅<Bi> films containing up to ~7 at.% Bi impurity, under laser irradiation, their structure undergoes a transition from an amorphous state to a thermodynamically stable crystalline state with a hexagonal structure through an intermediate metastable crystalline state with a cubic structure. In Ge₂Sb₂Te₅<Bi> films with a higher Bi concentration under laser irradiation, their structure is made from an amorphous state to a crystalline state with a stable hexagonal structure without an intermediate metastable state.