Amorphous-to-crystalline transition in Ge8Sb(2-x)BixTe11 phase-change materials for data recording

• Crystallization behavior of Ge8Sb(2-x)BixTe11 thin films was studied by DSC.
• Sb → Bi substitution leads to a decrease of crystallization enthalpy and activation energy.
• All compositions exhibited very similar transformation kinetics.
• Rapidity of the crystallization process was quantified for the studied compositions.
• Highest crystallization speed was produced by the Ge8Sb0.8Bi1.2Te11 composition.

Structural and thermokinetic analyses were used to study the crystallization behavior of Ge8Sb(2-x)BixTe11thin films, promising materials for phase-change memory recording applications. By exploring the full compositional range, it was found that the Sb→Bi substitution leads to a decrease of crystallization enthalpy and activation energy of the main crystallization phase-change process. These trends were explained in terms of the changing structural ordering within the recently proposed new phase-change atomic switching mechanism. All of the compositions exhibited very similar transformation kinetics, confirming the uniformity of the phase-change mechanisms involved. It was further shown that rapid energy delivery achieved during heating, in the case of all investigated materials, leads to a transition from the classical nucleation/growth-based formation of 3D crystallites towards an autocatalytic phase-change process with an enormously increased speed of crystallization. Rapidity of the crystallization process was quantified for all of the studied compositions based on a novel Index of Crystallization Rapidity criterion – the results provided by this criterion showed that the highest crystallization speed was produced by the Ge8Sb0.8Bi1.2Te11 composition, which therefore from this point of view appears to be a suitable candidate for the new generation of phase-change memory recording devices.