Evolutionary design of interfacial phase change van der Waals heterostructuresElectronic supplementary information (ESI) available. See DOI: 10.1039/C6NR05539G

• Main Authors: Kalikka, Janne, Zhou, Xilin, Behera, Jitendra, Nannicini, Giacomo, Simpson, Robert E
• Format: Journal Article
• Language: English
• Published: 27.10.2016
• ISSN: 2040-3364; 2040-3372
• DOI: 10.1039/c6nr05539g

We use an evolutionary algorithm to explore the design space of hexagonal Ge 2 Sb 2 Te 5 ; a van der Waals layered two dimensional crystal heterostructure. The Ge 2 Sb 2 Te 5 structure is more complicated than previously thought. Predominant features include layers of Ge 3 Sb 2 Te 6 and Ge 1 Sb 2 Te 4 two dimensional crystals that interact through Te-Te van der Waals bonds. Interestingly, (Ge/Sb)-Te-(Ge/Sb)-Te alternation is a common feature for the most stable structures of each generation's evolution. This emergent rule provides an important structural motif that must be included in the design of high performance Sb 2 Te 3 -GeTe van der Waals heterostructure superlattices with interfacial atomic switching capability. The structures predicted by the algorithm agree well with experimental measurements on highly oriented, and single crystal Ge 2 Sb 2 Te 5 samples. By analysing the evolutionary algorithm optimised structures, we show that diffusive atomic switching is probable by Ge atoms undergoing a transition at the van der Waals interface from layers of Ge 3 Sb 2 Te 6 to Ge 1 Sb 2 Te 4 thus producing two blocks of Ge 2 Sb 2 Te 5 . Evolutionary methods present an efficient approach to explore the enormous multi-dimensional design parameter space of van der Waals bonded heterostructure superlattices. We use an evolutionary algorithm to explore the design space of hexagonal Ge 2 Sb 2 Te 5 ; a van der Waals layered two dimensional crystal heterostructure.