研究目的
Investigating the quantitative measurement of the electric potential, electric field, and charge density in a monolayer of MoS2 at atomic scale resolution using off-axis electron holography.
研究成果
The study demonstrates the feasibility of quantitatively measuring the local charge densities with atomic resolution in monolayers of 2D materials using high resolution off-axis electron holography. The methodology allows for the correction of drifts and aberrations, achieving a high signal-to-noise ratio that enables the direct calculation of charge density from phase images. The results are consistent with DFT simulations, validating the accuracy of the measurements.
研究不足
The need to take measurements near a region of vacuum makes the specimen less mechanically stable and dirty, complicating the finding of a suitable region of interest. The use of a single biprism system limits the field of view and spatial resolution.
1：Experimental Design and Method Selection:
Off-axis electron holography was used with a double aberration-corrected transmission electron microscope operated at 80 kV and a low electron beam current density to limit specimen damage. Series of holograms were acquired to improve sensitivity.
2：Sample Selection and Data Sources:
Epitaxial monolayer MoS2 samples were grown by CVD onto c-plane sapphire and prepared for TEM analysis.
3：List of Experimental Equipment and Materials:
A double aberration-corrected FEI Titan Ultimate TEM operated at 80 kV, a 4k × 4k pixel2 Gatan OneView camera for recording holograms, and Holoview software for data processing.
4：Experimental Procedures and Operational Workflow:
A series of 89 electron holograms were acquired with a field of view of 33 nm and a fringe spacing of
5：077 nm, each for 4 seconds with a dead time of 1 second in-between. Data Analysis Methods:
The series of electron holograms were reconstructed with a spatial resolution of 0.24 nm, correcting for mechanical and optical drifts, and residual aberrations were corrected up to the third order.
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