Novel polymorphic phase of two-dimensional VSe2: The 1T′ structure and its lattice dynamics

Ganbat Duvjir, Byoung Ki Choi, Trinh Thi Ly, Nguyen Huu Lam, Seung Hyun Chun, Kyuha Jang, Aloysius Soon, Young Jun Chang, Jungdae Kim

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7 Citations (Scopus)


Polymorphisms allowing multiple structural phases are among the most fascinating properties of transition metal dichalcogenides (TMDs). Herein, the polymorphic 1T′ phase and its lattice dynamics for bilayer VSe2 grown on epitaxial bilayer graphene are investigated via low temperature scanning tunneling microscopy (STM). The 1T′ structure, mostly observed in group-6 TMDs, is unexpected in VSe2, which is a group-5 TMD. Emergence of the 1T′ structure in bilayer VSe2 suggests the important roles of interface and layer configurations, providing new possibilities regarding the polymorphism of TMDs. Detailed topographical analysis elucidates the microscopic nature of the 1T′ structure, confirming that Se-like and V-like surfaces can be resolved depending on the polarity of the sample bias. In addition, bilayer VSe2 can transit from a static state of the 1T′ phase to a dynamic state consisting of lattice vibrations, triggered by tunneling current from the STM tip. Topography also shows hysteretic behavior during the static-dynamic transition, which is attributed to latent energy existing between the two states. The observed lattice dynamics involve vibrational motion of the Se atoms and the middle V atoms. Our observations will provide important information to establish in-depth understanding of the microscopic nature of 1T′ structures and the polymorphism of two-dimensional TMDs.

Original languageEnglish
Pages (from-to)20096-20101
Number of pages6
Issue number42
Publication statusPublished - 2019 Nov 14

Bibliographical note

Funding Information:
This work is supported by National Research Foundation (NRF) grants funded by the Korean government (NRF-2018R1-D1A1B07050144, NRF-2019R1A6A1A11053838, NRF-2014R1-A4A1071686, and NRF-2017R1C1B2004927).

All Science Journal Classification (ASJC) codes

  • Materials Science(all)

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