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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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Size and strain effects on mechanical and electronic properties of green phosphorene nanoribbons
Recently, a phosphorus isomer named green phosphorus was theoretically predicted with a similar interlayer interaction compared to that of black phosphorus, thus indicating that individual layers can be mechanically exfoliated to form two-dimensional (2D) layers known as green phosphorene. In this work, we investigated the properties of green phosphorene nanoribbons along both armchair and zigzag directions with ribbon widths up to 57 Å using density functional theory. Effects of ribbon width and strain on the mechanical and electronic properties of the ribbons were studied. The Young’s modulus, effect of quantum confinement on the band gap, and effect of strain on the band structures of the ribbons were investigated. The green phosphorene ribbons were found to exhibit prominent anisotropic properties, with the Young’s modulus in the range of 10-35 GPa for the armchair green phosphorene nanoribbons (AGPNR) and 160-170 GPa for the zigzag green phosphorene nanoribbons (ZGPNR), which are the same order of magnitude as those of the 2D sheets. The work function was found to be between 5 eV ∼ 5.7 eV for the range of widths studied. Both size and strain trigger direct-indirect band gap transitions in the ribbons and their transition mechanisms were discussed.
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- Award ID(s):
- 1710017
- PAR ID:
- 10597218
- Publisher / Repository:
- American Institute of Physics
- Date Published:
- Journal Name:
- AIP Advances
- Volume:
- 8
- Issue:
- 11
- ISSN:
- 2158-3226
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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