Atomic Engineering of Triangular Nanopores in Monolayer hBN: A Decoupled Seeding and Growth Approach

TL;DR

This paper presents a novel decoupled seeding and growth method for fabricating precise, high-density triangular nanopores in monolayer hBN, combining ion and electron irradiation with thermal annealing for enhanced control and scalability.

Contribution

The study introduces a new decoupled approach for nanopore fabrication that improves size control, density, and scalability in 2D materials, particularly monolayer hBN.

Findings

Controlled nanopore size and density via irradiation doses

Real-time imaging of nanopore formation process

Thermal annealing enhances pore quality and removes contaminants

Abstract

Nanopores in 2D materials are of significant interest in advanced membrane technologies aimed at the sensing and separation of ions and molecules. These applications necessitate 2D nanopores that are precise in size and shape, and abundant in number. However, conventional fabrication techniques often struggle to achieve both high precision and throughput. In this study, we introduce a decoupled seeding and growth approach designed to overcome this limitation. The method allows the controlled fabrication of ensembles of nanopores with narrow size distribution and is demonstrated for free-standing monolayer hexagonal boron nitride. Using light ion showering, we first create vacancy defect seeds. These seeds are then expanded into triangular nanopores through element-specific preferential atom removal under broad-beam electron irradiation in a transmission electron microscope. Nanopore density and size are controlled by the ion and electron irradiation doses, respectively. During the electron irradiation step, high-resolution imaging allows real-time tracking of the nanopore formation process, enabling the highest level of control. An additional workflow is introduced using thermal annealing in air for the nanopore growth step, delivering the most flexible platform for nanopore fabrication over larger areas with the significant benefit of concurrently removing surface hydrocarbon contamination to mitigate pore clogging and distortion. This study provides researchers with a novel approach to create ensembles of meticulously designed nanopores with well-controlled size and geometry, facilitating the development of next-generation membrane devices that will demand high precision and high throughput nanopore fabrication pipelines.