Due to their unique electrical, optical, and magnetic properties, two-dimensional (2D) materials offer the potential for a wide range of applications in electronics and optoelectronics. However, pristine 2D materials with fixed features may not be able to meet the demands of multifunctional new applications. As a result, property tuning is critical. Alfa Chemistry can help customers achieve controlled property modulation by making atomic-scale structural changes to their 2D materials.
Due to thermal motion and lattice growth kinetics, different atomic scale structures (ASSs) can result from natural or intentional modulation of the atomic configuration of 2D materials. Shifts in ASSs can cause changes in charge density, electron density of states, and lattice symmetry, allowing 2D materials' properties to be tuned.
We have a lot of expertise with ASSs in controlled structural design and exact property tuning of 2D materials, particularly for atomic flaws and edge structures. Please contact us as soon as possible for the best assistance!
Classification of ASSs of 2D Materials
The shape and atomic arrangement of 2D materials are significantly influenced by ASSs. ASSs are divided into four categories based on their atomic configuration: grain boundaries (GBs), atomic defects, edge structures, and stacking patterns.
Alfa Chemistry researchers have recently focused on the formation mechanisms, design techniques, and performance modulation of atomic-level structural alterations in 2D materials. During synthesis or post-processing, we can purposefully incorporate some ASS into the resulting 2D materials. We also look at the possible formation mechanisms of ASSs in order to provide guidelines for controlled modification of 2D materials.
Fig 1. The design and application of ASSs of 2D materials. (Xiao Y, et al. 2019)
Design Strategies for ASSs 2D Material Modification
For accurate property tuning of 2D materials, controlled atomic-level structural modifications are required, which can be performed during chemical synthesis or after growth, notably for atomic defects and edge structures. The following sections outline our key design strategies and mechanisms.
Atomic Defect Design
We can intentionally design atomic defects and introduce them into two-dimensional materials. There are several ways for designing atomic defects with great controllability, including direct introduction and post-processing, to provide controlled tuning of characteristics.
- Direct introduction - During the synthesis of 2D materials, direct introduction refers to the direct management of each precursor's chemical potential, hence influencing reaction kinetics to produce atomic vacancies. Direct introduction is a good way to control the distribution of atomic flaws during 2D material synthesis.
- Post-treating - Post-treating is a common method for introducing atomic defects into the obtained 2D materials. Atomic defects can be introduced into the required region of the 2D material using high-energy plasma, ion/electron beam irradiation, or chemical media. Atomic doping achieved directly by post-treatment is usually applicable to stripped or obtained materials and includes plasma, chemical treatment, and ion/electron beam mediated doping.
Fig 2. Scheme of introduction of Se-vacancies to WSe2 via H2 or He plasma. (Tosun M, et al. 2016)
Edge Structure Design
Crystal growth kinetics are tightly linked to edge structures. We will provide several strategies for designing edge structures, including anisotropic etching, molecular assembly, lattice plane control, and chemical potential control.
- Anisotropic Etching - Anisotropic etching uses metal particles and a decreasing environment to create edge control from the top down.
- Molecular Assembly - Molecular assembly is commonly used for bottom-up synthesis of nanostructured 2D materials. Bottom-up techniques are mainly based on organic synthesis, starting with small molecular modules and then undergoing chemical reactions to form covalently linked 2D network structures.
- Lattice plane control - Control of the growing substrate's crystalline planar edge structure is more controllable based on crystal growth kinetics than - anisotropic etching and molecular assembly.
- Chemical potential control - The chemical potential of the precursor can have a strong influence on the edge ends and thus the crystal morphology.
References
- Xiao Y, et al. (2019). "Atomic-Scale Structural Modification of 2D Materials." Advance Science. 6(5): 1801501.
- Tosun M, et al. (2016). "Air-Stable n-Doping of WSe2 by Anion Vacancy Formation with Mild Plasma Treatment." ACS Nano. 10: 6853.
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