Defect-nucleated phase transition in atomically-thin WS2. (28th January 2021)

• Record Type: Journal Article
• Authors: Zhang, Zhenhua; Liu, Weiwei; Zhang, Bin; Sateesh, Bandaru; Yuan, Lijun; Zhu, Dancheng; Guan, Pengfei; Pennycook, Stephen J; Guo, Junjie
• Is Part Of: 2D materials. Volume 8:Number 2(2021)
• Publication Date: 2021-01-28
• Subjects: transmission electron microscopy -- atomic defects -- phase transitions -- 2D materials -- atomic and electronic structure; Graphene -- Periodicals; Materials science -- Periodicals; Nanostructured materials -- Periodicals; 620.115
• DOI: 10.1088/2053-1583/abd6b4
• Languages: English
• ISSNs: 2053-1583

Abstract

Abstract: Precise control of phase transitions in polymorphic 2D transition metal dichalcogenides (TMDs) is expected to play a key role in modern intelligent devices. However, an atomic-scale understanding and thus control of the phase transitions in the atomically-thin TMDs have not been reached, especially in some metastable phases. Here, in metastable monolayer 1T′ WS2, we demonstrate the dynamics of a phase transition nucleated from atomic defects by the means of time-resolved annular dark-field imaging and atomic-resolution electron energy-loss spectroscopy. It is found that the atomic and electronic structure of the 1T′ phase is inhomogeneous, which is decided by zone-dependent W–S bond strengths due to a Peierls-like structure distortion. Meanwhile, the W–S bonding is flexible to allow large nonequilibrium atom shifts for phase transition. Thus, just a few atomic defects can stabilize the atomic-scale nucleus of the new phase to initialize the phase transition from 1T′ to 1H locally. Our finding reveals the possibility of controlling the phase transitions in 2D materials by defect engineering.