Interface-dependent fragile-to-strong kinetic feature in two-dimensional confined phase-change nano-films

Abstract

In addition to conventional doping strategies, nano-structuring combined with interfacial engineering has recently emerged as a promising approach for enhancing phase-change material (PCM) performance. In this work, we comparatively investigate anomalous crystallization kinetics in two-dimensional (2D) confined Ge2Sb2Te5 (GST), GeTe, and Sb2Te3 nano-films using flash differential scanning calorimetry, with tungsten (W) serving as the confining layer. We observe that both GST and GeTe nano-films exhibit distinct fragile-to-strong crossover (FSC) behavior under 2D confinement, while Sb2Te3 shows no FSC regardless of confinement. The presence of FSC behavior helps alleviate the trade-off between fast crystallization near the melting temperature and high thermal stability near the glass transition temperature. Time–temperature–transformation curves reveal that 2D confined GST achieves crystallization in only 3.4 ns at 680 K, outperforming GeTe (17 ns at 626 K) and Sb2Te3 (257 ns at 668 K). The occurrence or absence of FSC is attributed to interfacial bonding differences, i.e., strong W–Ge bonds promote FSC, whereas weak W–Te and/or W–Sb interactions do not. These results highlight the role of interface-engineered 2D confinement in tailoring PCM crystallization kinetics, offering perspectives for advanced memory applications.