Crystallization of thin films GST alloy under the action of ultrashort pulse laser radiation

The paper presents electrical resistivity and optical transmission and reflection coefficients of thin films of Ge2Sb2Te5 (GST) alloy thin films changing dynamics during the femtosecond laser radiation induced crystallization studying results. It is shown that the most effective of ultrashort laser pulses on the phase state of the film is a multi-pulse mode, which is associated with a high stochasticity of GST crystallization. It is experimentally demonstrated that for films thicker than 100 nm, the most accurate control of the crystalline phase fraction is obtained at energy densities from 10 to 20 mJ/cm2. The switching time of the electrical properties does not exceed 100 ns, which is due to the formation of conducting crystalline paths in the film material. The dynamics of the optical properties allows to distinguish two time sections. The sharp jump can be explained by both the increase in carrier concentration and the process of recalescence and reamorphization. The slow relaxation is explained by the formation of the crystalline phase (nucleation and crystallite growth). An important result is the experimental detection of X-ray diffraction peaks of a new crystalline phase (simple cubic phase). The formation of this phase is related both to the rearrangement of the atomic structure and to the depletion of the formation of chemical bonds due to the interaction of electrons with ultrashort duration radiation.