Customizing the features and functionality of two-dimensional (2D) substances is inextricably linked to defect engineering. Traditional techniques, particularly in non-vacuum settings, do not provide the required control to incorporate and investigate defects in 2D substances.
Study: Enhancing Infrared Light–Matter Interaction for Deterministic and Tunable Nanomachining of Hexagonal Boron Nitride. Image Credit: Quality Stock Arts/Shutterstock.com
A recent study published in the journal Nano Letters focuses on this issue by enhancing light-matter interaction for tunable nanomachining of hexagonal boron nitride (hBN) using atomic force microscopy (AFM). The research also investigates stimulated lattice deformations using nano-infrared spectroscopy.
Defect Engineering in 2D Materials: Overview and Applications
The importance of two-dimensional (2D) materials has significantly increased from both a theoretical and practical perspective due to the remarkable electrical properties of 2D graphene, transition metallic dichalcogenides, and hexagonal boron nitride (hBN).
The effect of these substances on the functionality of energy storage systems has been made evident over the past decade. As in the cases of engineered faults in hBN and defect-mediated development of graphene, innovative features and functions can be added to 2D materials while preserving their conformational advantages using nanomachining.
Nanomachining provides novel techniques for constructing 2D materials for optoelectronic devices, catalyst supports, and quantum communication applications. Carefully chosen hBN defects exhibit quantum behavior at ambient temperature, offering a new framework for complex 2D quantum equipment.
Recently developed theoretical approaches predict that nanomachining causes the introduction of heavily correlated electronic regimes in hBN. In this regard, structural distortions must be created and tuned at specific points when manipulating 2D layers experimentally.
Limitations of Current Defect Engineering Techniques
Defects in hBN, aside from those naturally brought on by surface modification, are usually manufactured by ion implantation, electronic radiation exposure, mechanical refining, or thermal heat treatment. These energy-intensive nanomachining methods lead to the creation of surface defects and obstruct the in-depth analysis of specific features.
Additionally, standard diagnostic techniques like optical spectrophotometer, mass spectroscopy, and X-ray photoluminescence spectroscopy are used to evaluate the response of induced defects.
These methods offer averaged data about the investigated volume, which covers a sizable area of undisturbed substance. However, these methods cannot currently differentiate between the fingerprint of a local defect and its impact on the local characteristics of the metal.
It is usually difficult to use equipment with nanosized resolving strength, such as transmission electron microscopy (TEM), for in situ laboratory testing of 2D structures. TEM offers an ultra-high definition image of materials' crystalline lattice. However, the chemical image required to comprehend the local reactions occurring at defect sites is not provided by in vacuo spectrometry conducted in the TEM.
Novel Nanomachining Techniques for Defect Engineering
Scanning probe microscopy (SPM) and other novel nanomachining methods have recently been created for defect engineering of 2D nanomaterials.
Breakthroughs in operational SPM, such as light-matter interaction and nano-infrared spectroscopy, enable the constrained formation of imperfections on 2D materials. However, few scientific studies have used nano-infrared spectroscopy to observe local chemical reactions at a catalytic site.
In this study, the researchers created and studied local nanosized lattice imperfections in 2D materials using the light-matter interaction properties of atomic force microscopy (AFM) and nano-infrared spectroscopy.
The mechanism of light-matter interaction near the AFM tip was studied, along with the effects of incident beam power, time of exposure, and environmental factors. Nano-infrared spectroscopy was used to characterize the modifications in chemical fingerprints affiliated with defect formation.
Key Developments of the Current Study
It was discovered that nano-infrared spectroscopy could be used to effectively designate fingerprints to defects found in 2D hBN flakes, such as wrinkles, corners, and nanoholes. The infrared patterns accumulated by nano-infrared spectroscopy provide extensive data about the strain threshold in the lattice and the deformation caused by honeycomb lattice disturbance.
Additionally, the capability to alter light-matter interaction at the AFM tip allowed for the incorporation of defects into the hBN surface. This manipulation of light-matter interaction offers a powerful strategy for defect engineering in other 2D materials, with temporal, structural, and chemical influences that customary defect techniques cannot match.
Based on these findings, it is reasonable to conclude that the light-matter interaction and nano-infrared spectroscopy-based nanomachining approach used in this study can facilitate predictive control of chemical composition in 2D materials for applications such as optoelectronics and quantum detection.
Torres-Davila, F. E. et al. (2022). Enhancing Infrared Light–Matter Interaction for Deterministic and Tunable Nanomachining of Hexagonal Boron Nitride. Nano Letters. Available at: https://pubs.acs.org/doi/10.1021/acs.nanolett.2c02841
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