Designing Multiple Crystallization in Superlattice-like Phase-Change Materials for Multilevel Phase-Change Memory

Long Zheng; Wenxiong Song; Zhitang Song; Sannian Song

doi:10.1021/acsami.9b16876

Designing Multiple Crystallization in Superlattice-like Phase-Change Materials for Multilevel Phase-Change Memory

ACS Appl Mater Interfaces. 2019 Dec 11;11(49):45885-45891. doi: 10.1021/acsami.9b16876. Epub 2019 Dec 3.

Authors

Long Zheng^{1

2}, Wenxiong Song¹, Zhitang Song¹, Sannian Song¹

Affiliations

¹ State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Micro-System and Information Technology , Chinese Academy of Sciences , Shanghai 200050 , China.
² School of Mathematics and Physics , Jiangsu University of Technology , Changzhou 213001 , China.

PMID: 31749358
DOI: 10.1021/acsami.9b16876

Abstract

A multilevel phase-change memory device was successfully designed, which was fabricated using a Ge₄₀Te₆₀/Cr superlattice-like (SLL) structure. In the SLL films, a two-step phase change process is observed at elevated temperatures, which reveals the crystallization of Ge₄₀Te₆₀ (GT) and an interface-dominated formation of Cr₂Ge₂Te₆ (CrGT). The bonding of Cr-Te and Ge-Ge is accompanied by the breaking of a Ge-Te bond, which is mainly in the Ge-rich GeTe_4-nGe_n units. The formation of CrGT is related to the breaking apart of the edge-sharing octahedron in GT and Cr replacement at Ge sites. The crystalline GT acts as the crystallization precursors in the formation of the CrGT phase. The stable reversible two-step phase change can guarantee the reliability of the multilevel storage. The present work may shed light on the possible mechanism of the CrGT phase transition-based interfacial dynamic process. The designed multiple crystallization system demonstrates a potential for multilevel storage.

Keywords: Cr−Ge−Te; Ge−Te; crystallization; interface; multilevel phase-change memory; superlattice-like structure.