Direct visualization of the 3D structure of silicon impurities in graphene

TL;DR

This study employs aberration-corrected STEM to directly visualize and analyze the 3D structure and dynamic behavior of silicon impurities in graphene, revealing out-of-plane configurations and atomic switching.

Contribution

It provides the first direct 3D visualization of silicon impurities in graphene and demonstrates their dynamic switching between configurations.

Findings

Silicon atoms switch between up- and down- configurations.

Asymmetry in atomic positions reveals non-planarity.

Direct observation of silicon tetramer structures.

Abstract

We directly visualize the three-dimensional (3D) geometry and dynamics of silicon impurities in graphene as well as their dynamics by aberration-corrected scanning transmission electron microscopy. By acquiring images when the sample is tilted, we show that an asymmetry of the atomic position of the heteroatom in the projection reveals the non-planarity of the structure. From a sequence of images, we further demonstrate that the Si atom switches between up- and down- configurations with respect to the graphene plane, with an asymmetric cross-section. We further analyze the 3D structure and dynamics of a silicon tetramer in graphene. Our results clarify the out-of-plane structure of impurities in graphene by direct experimental observation and open a new route to study their dynamics in three dimensions.