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We performed a comprehensive first-principles study on the structural and electronic properties of ZnSe two-dimensional (2D) nanosheets and their derived one-dimensional (1D) nanoribbons (NRs) and nanotubes (NTs). Both hexagonal and tetragonal phases of ZnSe (h-ZnSe and t-ZnSe) were considered. The tetragonal phase is thermodynamically more favorable for 2D monolayers and 1D pristine ribbons, in contrast, the hexagonal phase is preferred for the edge-hydrogenated 1D NRs and NTs. The 2D h-ZnSe monolayer is a direct-bandgap semiconductor. Both the pristine zigzag nanoribbons (z-hNRs) and the corresponding edge-hydrogenated NRs gradually convert from the direct-bandgap semiconducting phase into a metallic phase as the ribbon width increases; the pristine armchair nanoribbons (a-hNRs) remain as semiconductors with indirect bandgaps with increasing ribbon width, and edge hydrogenating switches the indirect-bandgap feature to the direct-bandgap character or the metallic character with different edge passivation styles. The 1D h-ZnSe single-walled nanotubes in both armchair and zigzag forms keep the direct-bandgap semiconducting property of the 2D counterpart but with smaller band gaps. For the thermodynamically more favorable t-ZnSe monolayer, the intrinsic direct-bandgap semiconducting character is rather robust: the derived 1D nanoribbons with edges unsaturated or hydrogenated fully, and 1D single-walled nanotubes all preserve the direct-bandgap semiconducting feature. Our systemic study provides deep insights into the electronic properties of ZnSe-based nanomaterials and is helpful for experimentalists to design and fabricate ZnSe-based nanoelectronics.
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Thermodynamics and electronic structure of edges in monolayer MoSi2N4
MoSi2N4 is a two-dimensional ternary nitride semiconductor that has attracted attention for its excellent mechanical and thermal properties. Theoretical studies predict that zigzag edges of this material can host magnetic edge states and Dirac fermions, but the stability of such edges has not been examined. Here, we present a density functional theory study of the electronic and thermodynamic properties of MoSi2N4 edges. We develop a (partial) ternary phase diagram that identifies a region of chemical potentials within which MoSi2N4 is stable over competing elemental or binary phases. Based on this phase diagram, we determine the thermodynamic stability of several armchair and zigzag edges and elucidate their electronic structures. Bare zigzag edges, predicted to host exotic electronic states, are found to be substantially higher in energy than armchair edges and, thus, unlikely to occur in practice. However, with hydrogen passivation, these zigzag edges can be stabilized relative to their armchair counterparts while retaining metallicity and magnetic order. Our analysis provides a solid thermodynamic basis for further exploration of MoSi2N4 in nanoscale electronics and spintronics.
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- Award ID(s):
- 1803614
- PAR ID:
- 10544262
- Publisher / Repository:
- AIP
- Date Published:
- Journal Name:
- Journal of Applied Physics
- Volume:
- 136
- Issue:
- 3
- ISSN:
- 0021-8979
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1063/5.0218366
