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Electron Beam Guides Engineering of Functional Defects

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Shown is a Z-contrast image of a vacancy-induced inversion domain (highlighted by the large yellow triangle) embedded in the hexagonal lattice of a monolayer of MoSe2.
The electron beam of a scanning transmission electron microscope was applied to generate Se vacancies in a semiconducting monolayer of MoSe2, provide energy to drive the formation and growth of inversion domains and metallic 60¡ grain boundaries, and track the dynamics. These results demonstrate it is possible to construct and characterize functional defects in monolayer materials via controllable electron-beam-guided vacancy engineering.

Grain boundaries with 60¡ tilt-angle in semiconducting transition-metal dichalcogenide (TMDC) monolayers display metallic behavior and can drastically quench local photoluminescence. Fundamental understanding of the atomic mechanism for the formation and dynamics of the inversion domains and 60¡ grain boundaries provides the keys to tuning the electronic and optical properties of monolayer TMDC materials via defect engineering. Electron microscopy and density functional theory revealed that the segregation of Se vacancies induced atomic displacement that led to the nucleation and growth of inversion domains and 60¡ grain boundaries. The researchers also demonstrated large-scale creation of inversion domains by high-temperature annealing, in which thermal energy activated similar defect evolution.

 

J. Lin, S. T. Pantelides, and W. Zhou, “Vacancy-Induced Formation and Growth of Inversion Domains in Transition-Metal Dichalcogenide Monolayer,” ACS Nano (2015).     DOI: 10.1021/acsnano.5b00554

 

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