Van der Waals interfacial bonding and intermixing in GeTe-Sb2Te3-based superlattices

• Published in: Nano research Vol. 11; no. 3; pp. 1676 - 1686
• Main Authors: Lotnyk, Andriy, Hilmi, Isom, Ross, Ulrich, Rauschenbach, Bernd
• Format: Journal Article
• Language: English
• Published: Beijing Tsinghua University Press 01.03.2018; Springer Nature B.V
• Subjects: Atomic structure; Atomic/Molecular Structure and Spectra; Biomedicine; Biotechnology; Bonding; Cations; Chemistry and Materials Science; Condensed Matter Physics; Crystal structure; Data storage; Germanium antimonides; Interlayers; Materials Science; Nanotechnology; Phase change materials; Pulsed laser deposition; Research Article; Scanning transmission electron microscopy; Silicon substrates; Superlattices; Switching; Transmission electron microscopy; 超点阵;混合;界面;分析电子显微镜;合并;水晶结构;应用程序;数据存储; Cs-corrected scanning transmission electron microscopy; intermixing; interfacial phase change memory (iPCM); thin films
• ISSN: 1998-0124; 1998-0000
• DOI: 10.1007/s12274-017-1785-y

Interfacial phase change memory （iPCM） based on GeTe and Sb2Te3 superlattices （SLs） is an emerging contender for non-volatile data storage applications. A detailed knowledge of the atomic structure of these materials is crucial for further development of SLs and for a better understanding of the resistivity switching characteristics of iPCM devices. In this work, crystalline GeTe-Sb2TeB- based SLs, produced by pulsed laser deposition onto a Si（111） substrate at temperatures lower than in previous studies, are analyzed by advanced scanning transmission electron microscopy. The results reveal the formation of Ge-rich Ge（x＋y）Sb（2-y）Tez building blocks with specific numbers of ordered Ge cation layers （between I and 5） and disordered cation layers （4） for z = 6-10, as well as intermixed cation layers for z = 5, within the SLs. The G Ge（x＋y）Sb（2-y）Tez units are separated from the Sb2Te3 building blocks by van der Waals gaps. In particular, the interlayer bonding is promoted by the formation of outermost cation layers consisting of intermixed GeSb within the building blocks adjacent to the van der Waals gaps. The Ge（x＋y）Sb（2-y）Tez units with z 〉 5 retain metastable crystal structures with two-dimensional bonding within the SLs. The present study shed new light on the possible configurations of the building units that can be formed during the synthesis of GeTe-Sb2Te3-based iPCM materials. In addition, a possible switching mechanism active in iPCM materials is discussed.