Characterization of LiBC by phase-contrast scanning transmission electron microscopy

Area of Science:

• Materials Science
• Solid-State Chemistry
• Electron Microscopy

Background:

• Lithium-boron-carbon (LiBC) compounds feature hetero graphite layers with intercalated lithium.
• Visualizing lithium distribution at the atomic scale is crucial for understanding material properties.
• Aberration-corrected scanning transmission electron microscopy (STEM) offers high-resolution imaging capabilities.

Purpose of the Study:

• To evaluate the applicability of phase-contrast (PC) imaging in aberration-corrected STEM for visualizing lithium distribution in LiBC.
• To correlate experimental PC-STEM images with theoretical simulations.
• To investigate potential lithium atom displacement under electron beam irradiation.

Main Methods:

• Utilized phase-contrast (PC) imaging in an aberration-corrected scanning transmission electron microscope (STEM).
• Employed LiBC as a model compound.
• Performed multi-slice simulations based on the reciprocity principle.
• Analyzed the defocus dependence of experimental images.

Main Results:

• PC-STEM images successfully reflected the crystal structure of LiBC, particularly the arrangement of boron, carbon, and lithium.
• Experimental images and their defocus dependence closely matched the multi-slice simulations.
• Observed that some lithium positions were unoccupied, suggesting electron beam-induced lithium displacement.

Conclusions:

• Phase-contrast imaging in aberration-corrected STEM is a viable technique for visualizing lithium distribution in materials like LiBC.
• Multi-slice simulations are effective in interpreting PC-STEM images.
• Intense electron beam exposure can lead to lithium atom displacement in the LiBC structure.