Abstract
Two-dimensional (2D) materials are promising candidates for uses in next-generation electronic and optoelectronic devices. However, only a few high-quality 2D materials have been mechanically exfoliated to date. One of the critical issues is that the exfoliability of 2D materials from their bulk precursors is unknown. To assess the exfoliability of potential 2D materials from their bulk counterparts, we derived an elasticity-based-exfoliability measure based on an exfoliation mechanics model. The proposed measure has a clear physical meaning and is universally applicable to all material systems. We used this measure to calculate the exfoliability of 10,812 crystals having a first-principles calculated elastic tensor. By setting the threshold values for easy and potential exfoliation based on already-exfoliated materials, we predicted 58 easily exfoliable bulk crystals and 90 potentially exfoliable bulk crystals for 2D materials. As evidence, a topology-based algorithm indicates that there is no interlayer bonding topology for 93% predicted exfoliable bulk crystals, and the analysis on packing ratios shows that 99% predicted exfoliable bulk crystals exhibit a relatively low packing ratio value. Moreover, literature survey shows that 34 predicted exfoliable bulk crystals have been experimentally exfoliated into 2D materials. In addition, the characteristics of these predicted 2D materials were discussed for practical use of such materials.
Highlights
Two-dimensional (2D) materials with ultimate thinness are highly promising for applications in next-generation electronic, optoelectronic devices, and macroscopic assemblies, benefiting from their extreme structures and properties[1,2,3,4,5,6,7]
The accumulated knowledge of structureproperty has been collected in databases such as the Pauling file[16], the Inorganic Crystal Structure Database (ICSD)[17,18], the Crystallographic Open Database (COD)[19], the Computational 2D Materials Database (C2DB)[20], and Materials Project (MP)[21]
Considering the requirement of a high in-plane strength and a weak interlayer interaction for mechanically exfoliable 2D materials, Gao et al.[30] derived a dimensionless measure σs/γ based on an exfoliation mechanics model, where σs and γ are the in-plane 2D strength and the interlayer binding energy, respectively
Summary
Two-dimensional (2D) materials with ultimate thinness are highly promising for applications in next-generation electronic, optoelectronic devices, and macroscopic assemblies, benefiting from their extreme structures and properties[1,2,3,4,5,6,7]. The lower the binding energy is, the easier the 2D materials can be exfoliated from the bulk counterparts[29] This intuition may break down since it does not consider the in-plane mechanical resistance of 2D materials (Fig. 1, the non-exfoliable layered crystal)[30]. Considering the requirement of a high in-plane strength and a weak interlayer interaction for mechanically exfoliable 2D materials, Gao et al.[30] derived a dimensionless measure σs/γ based on an exfoliation mechanics model, where σs and γ are the in-plane 2D strength (the fracture force divided by the width of 2D sheet) and the interlayer binding energy, respectively. The characteristics of these predicted 2D materials were discussed for practical applications
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