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Research Highlight

Low-Energy Implantation into Transition Metal Dichalcogenide Monolayers to form Janus Structures

Topic:

https://acs.altmetric.com/details/84678496/news

Selenium atoms, represented by orange, implant in a monolayer of blue tungsten and yellow sulfur to form a Janus layer. In the background, electron microscopy confirms atomic positions. Credit: Oak Ridge National Laboratory, U.S. Dept. of Energy
Selenium atoms, represented by orange, implant in a monolayer of blue tungsten and yellow sulfur to form a Janus layer. In the background, electron microscopy confirms atomic positions. Credit: Oak Ridge National Laboratory, U.S. Dept. of Energy

PI: Dave Geohegan

The selective conversion of an atomically thin 2D crystal to form a Janus monolayer was achieved by the hyperthermal implantation of clusters generated by laser ablation. Hyperthermal implantation of atomically thin 2D crystals presents a new, low-temperature synthesis method to form novel Janus structures, alloys, and metastable phases that have unique quantum properties desired for future applications in sensing, computing, or catalysis.

Selenium clusters were produced by laser ablation of Se targets, forming an energetic plasma  plume. The fast clusters were controllably slowed from 42 eV/atom by collisions with background argon gas  and directed to impinge on suspended crystals of monolayer WS2. A combination of atomic-resolution electron microscopy, molecular dynamic simulations, and first principles calculations provided understanding that revealed a kinetic energy window of 3-5 eV/atom for highly selective implantation of the clusters that converted only top-layer sulfur atoms to selenium—thus forming high-quality WSSe Janus monolayers.

Related Publication:

Y.-C. Lin, C. Liu, Y. Yu, E. Zarkadoula, M. Yoon, A. A. Puretzky, L. Liang, X. Kong, Y. Gu, A. Strasser, H. M. Meyer III, M. Lorenz, M. F. Chisholm, I. N. Ivanov, C. M. Rouleau, G. Duscher, K. Xiao, and D. B. Geohegan, Low-energy implantation into transition metal dichalcogenide monolayers to form Janus structures, ACS Nano 14, 3896 (2020), DOI: 10.1021/acsnano.9b10196.