Quantitative insights into the growth mechanisms of nanopores in hexagonal boron nitride

Abstract

The formation of nanopores under electron irradiation is an ideal process to quantify chemical bonds in 2D materials. Nowadays, High Resolution Transmission Electron Microscopy (HRTEM) allows investigating such nucleation and growth phenomena with incomparable spatial and temporal resolution. Moreover, theoretical calculations are usually exploited to confirm characteristic features of these atomicscale observations. Nevertheless, the full understanding of the ejection mechanisms of atoms requires studying in details the interplay between the very dynamic edge structure of expanding nanopores and the displacement energy of edge atoms (E D). Here, the dynamics of triangular nanopores in hexagonal boron nitride (h-BN) under various electron dose rates was followed by aberration-corrected HRTEM with high 2 temporal resolution to provide new in situ insights into their growth processes. We notably reveal that the ejection of atomic pairs is an elemental mechanisms that considerably speeds up the expansion of nanopores. Atomic-scale calculations were exploited to quantify the structure-dependent E D of all the ejected edge atoms. They revealed strong variations of this threshold energy during the growth processes. This quantitative study reconciles theoretical and experimental measurements of the ejection rate of atoms in h-BN under electron irradiation which is essential for nanopore engineering in this atomically-thin membrane.

Enhancing Infrared Light–Matter Interaction for Deterministic and Tunable Nanomachining of Hexagonal Boron Nitride

“…While the current spatial resolution of nano-IR spectroscopy cannot resolve atomic arrangements, the results suggest that flakes edges are passivated with B–OH bonds, though with varying local environments, especially at nonlinear cleavage regions (point 3) and corners (point 4). Theoretical models have considered numerous potential edge conformations in h -BN, in agreement with our experimental results. − …”

Electron beam-induced nanopores in Bernal-stacked hexagonal boron nitride

“…Furthermore, experimental studies aimed at locally probing the electronic structure at the edge are needed to complete our understanding of these systems. The most commonly observed edge type in h-BN is the nitrogen-terminated zigzag edge (N-edge) [10,[19][20][21][22][23][24][25], shown in Figure 2. By the application of a high-energy electron beam in a transmission electron microscopy (TEM) chamber, it is possible to fabricate the N-edge almost exclusively among all edge types [9,[26][27][28][29].…”

A deep learning approach for determining the chiral indices of carbon nanotubes from high-resolution transmission electron microscopy images

“…There is no doubt that our approach will be useful for other fields of research related to nanotubes but also in nanoscience more generally. The approach implemented can clearly be adapted to other nano-objects such as the structure of nanoparticles (pure, bimetallic, twins) 71 , characterization of defects in 2D materials 72 or identification of stacking in Van der Waals heterostuctures [73][74][75] .…”