Insights into ultrafast Ge-Te bond dynamics in a phase-change superlattice

• Published in: arXiv.org 2016-05
• Main Authors: Malvestuto, Marco, Caretta, Antonio, Casarin, Barbara, Cilento, Federico, Dell'Angela, Martina, Fausti, Daniele, Calarco, Raffaella, Kooi, Bart J, Varesi, Enrico, Robertson, John, Parmigiani, Fulvio
• Format: Article
• Language: English
• Subjects: Chalcogenides; Data storage; First principles; Overheating; Phase change materials; Phase transitions; Structural strain; Superlattices; Ultrafast lasers; X ray absorption
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1605.08157

A long-standing question for avant-grade data storage technology concerns the nature of the ultrafast photoinduced phase transformations in the wide class of chalcogenide phase-change materials (PCMs). Overall, a comprehensive understanding of the microstructural evolution and the relevant kinetics mechanisms accompanying the out-of-equilibrium phases is still missing. Here, after overheating a phase-change chalcogenide superlattice by an ultrafast laser pulse, we indirectly track the lattice relaxation by time resolved X-ray absorption spectroscopy (tr-XAS) with a sub-ns time resolution. The novel approach to the tr-XAS experimental results reported in this work provides an atomistic insight of the mechanism that takes place during the cooling process, meanwhile a first-principles model mimicking the microscopic distortions accounts for a straightforward representation of the observed dynamics. Finally, we envisage that our approach can be applied in future studies addressing the role of dynamical structural strain in phase-change materials.