Atomic Structure and Dynamics of Self-Limiting Sub-Nanometer Pores in Monolayer WS<sub>2</sub>
Name
acsnano.8b07051.pdf
Description
Accepted version
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3.24 MB
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Checksum (MD5)
021fff90d5b82b1ce88a2d50f2d3656b
Author(s)
Ryu, Gyeong Hee
France-Lanord, Arthur
Wen, Yi
Zhou, Si
Grossman, Jeffrey C.
Warner, Jamie H.
Date Issued
October 2018
Journal
ACS Nano
Publisher
American Chemical Society (ACS)
Version
Author's final manuscript
Abstract
© 2018 American Chemical Society. We reveal a self-limiting mechanism during the formation of a specific type of circular nanopore in monolayer WS2 that limits its diameter to sub-nm. A single W atom vacancy (triangular nanopore) is transformed into the self-limiting nanopore (SLNP) through the atomic restructuring of S atoms around the area, reducing the number of dangling bonds at the nanopore edge by shifting them further in-plane with W-W bonding instead. Bond rotations in WS2 help accommodate the electron beam induced atomic loss and ensure the stability of the SLNP. The SLNP shows significant improvement in diameter stability during electron beam irradiation compared to other triangular nanopores in WS2 that typically continue to expand in diameter during atom loss. The atomic structure of these SLNPs is studied using aberration-corrected scanning transmission electron microscopy with an in situ heating holder, revealing that the SLNPs are mostly formed at a temperature of -500 °C, which is a balance between thermally activated S vacancy diffusion and sufficient S vacancy density to initiate local atomic reconstruction. At higher temperatures (i.e., 1000 °C), S vacancies quickly migrate away into long line vacancies, resulting in low S vacancy density and rapidly expanding holes generated at the edges of the line vacancies. At room temperature, S vacancy migration is low and vacancy density is very high, which limits atomic reconstruction, and instead many small holes open up. These results provide insights into the factors that lead to uniform sized nanopores in the sub-nm range in transition-metal dichalcogenides.
MIT Department
Massachusetts Institute of Technology. Department of Materials Science and Engineering
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DOI of Published Version
https://doi.org/10.1021/acsnano.8b07051
