Revealing the crystallization kinetics of melt-quenched GeTe for realistic phase-change memory applications

The crystallization kinetics of as-deposited phase-change materials (PCMs) have been studied extensively. However, in real phase-change cells, PCMs must undergo a melt quenching process and be in an amorphous state. In this study, we performed the electron-beam evaporation method to obtain and simulate re-amorphous GeTe PCMs in real phase-change cells. We then investigated the crystallization kinetics of this melt-quenched GeTe material by analyzing the crystallization temperatures measured over a wide heating rate range (from 1 to 40,000 K s-1 ). Compared with the crystallization kinetics of as-deposited GeTe, the melt-quenched GeTe exhibits more fragile supercooled liquids with more distinct relaxation and a larger fragility index of 140. Moreover, the larger crystal growth rate and steady-state nucleation rate of melt-quenched GeTe result in faster total crystallization speed. We constructed the time-temperature-transformation curves for both melt-quenched and as- deposited GeTe, which indicate that the shortest crystallization time of melt-quenched GeTe is 4.1 ns at 633 K, approximately 20 times shorter than that of as-deposited GeTe (77.9 ns at 666 K). This was confirmed by characterizing the resistance-voltage curves in GeTe-based phase-change cells. Investigating the crystallization kinetics of melt-quenched GeTe not only enhances our understanding of PCMs in real phase-change cells but also advances the development of phase-change neuro-inspired computing.