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Robust Direct Bandgap Characteristics of One- and Two-Dimensional ReS2.

Yu ZG, Cai Y, Zhang YW - Sci Rep (2015)

Bottom Line: Two-dimensional (2D) transition-metal dichalcogenides (TMDs), most notably, MoS2 and WS2, have attracted significant attention due to their sizable and direct bandgap characteristics.In addition, the direct bandgap of ReS2 nanoribbons is only weakly dependent on their width.These robust characteristics strongly suggest that ReS2 has great potential for applications in optoelectronic nanodevices.

View Article: PubMed Central - PubMed

Affiliation: Institute of High Performance Computing, Singapore 138632, Singapore.

ABSTRACT
Two-dimensional (2D) transition-metal dichalcogenides (TMDs), most notably, MoS2 and WS2, have attracted significant attention due to their sizable and direct bandgap characteristics. Although several interesting MoS2 and WS2-based optoelectronic devices have been reported, their processability and reproducibility are limited since their electrical properties are strongly dependent of the number of layers, strain and sample sizes. It is highly desirable to have a robust direct bandgap TMD, which is insensitive to those factors. In this work, using density functional theory, we explore the effects of layer number, strain and ribbon width on the electronic properties of ReS2, a new member in the TMD family. The calculation results reveal that for monolayer ReS2, the nature (direct versus indirect) and magnitude of its bandgap are insensitive to strain. Importantly, the predicted bandgap and also charge carrier mobilities are nearly independent of the number of layers. In addition, the direct bandgap of ReS2 nanoribbons is only weakly dependent on their width. These robust characteristics strongly suggest that ReS2 has great potential for applications in optoelectronic nanodevices.

No MeSH data available.


Related in: MedlinePlus

The calculated projected density of states of RY-S8Re4 NR.The inset is the ReS6 octahedral complex.
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f6: The calculated projected density of states of RY-S8Re4 NR.The inset is the ReS6 octahedral complex.

Mentions: The weak distortion and high stability of RY-S8Re4 NR are due to its unique structure: ReS2 has the distorted CdCl2-type layer structure, with each Re atom bonding with 6S atoms, forming an octahedral complex (ReS6) as shown in the inset of Fig. 6. The slight increase in bond length along the six directions and odd valence electrons from Re (5d56s2) may result in the elongated Jahn-Teller distortions when degeneracy is broken. The d7 electronic configuration of Re provides one electron in the two degenerate eg orbitals ( and ), which involve in the degeneracy point directly at S, leading to doubly degenerate electronic ground states. Hence, a distortion may further enhance an energetic stability, which can be proved by analyzing the projected density of states (PDOS) in RY-S8Re4 NR as shown in Fig. 6. It is seen that Re-dxy and orbitals have significant overlap with S-p orbitals. When such an elongation occurs in ReS2 NRs, this may push the antibonding orbital Re- to a higher energy level and bonding orbitals Re-dxz and/or Re- to a lower energy level, causing ReS2 NRs to be more energetically stable. In contrast to other TMDs-based NRs, such as MoS2 NRs, it was reported that a large distortion was found in edges during the structure optimization even using hydrogen saturation11.


Robust Direct Bandgap Characteristics of One- and Two-Dimensional ReS2.

Yu ZG, Cai Y, Zhang YW - Sci Rep (2015)

The calculated projected density of states of RY-S8Re4 NR.The inset is the ReS6 octahedral complex.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4562306&req=5

f6: The calculated projected density of states of RY-S8Re4 NR.The inset is the ReS6 octahedral complex.
Mentions: The weak distortion and high stability of RY-S8Re4 NR are due to its unique structure: ReS2 has the distorted CdCl2-type layer structure, with each Re atom bonding with 6S atoms, forming an octahedral complex (ReS6) as shown in the inset of Fig. 6. The slight increase in bond length along the six directions and odd valence electrons from Re (5d56s2) may result in the elongated Jahn-Teller distortions when degeneracy is broken. The d7 electronic configuration of Re provides one electron in the two degenerate eg orbitals ( and ), which involve in the degeneracy point directly at S, leading to doubly degenerate electronic ground states. Hence, a distortion may further enhance an energetic stability, which can be proved by analyzing the projected density of states (PDOS) in RY-S8Re4 NR as shown in Fig. 6. It is seen that Re-dxy and orbitals have significant overlap with S-p orbitals. When such an elongation occurs in ReS2 NRs, this may push the antibonding orbital Re- to a higher energy level and bonding orbitals Re-dxz and/or Re- to a lower energy level, causing ReS2 NRs to be more energetically stable. In contrast to other TMDs-based NRs, such as MoS2 NRs, it was reported that a large distortion was found in edges during the structure optimization even using hydrogen saturation11.

Bottom Line: Two-dimensional (2D) transition-metal dichalcogenides (TMDs), most notably, MoS2 and WS2, have attracted significant attention due to their sizable and direct bandgap characteristics.In addition, the direct bandgap of ReS2 nanoribbons is only weakly dependent on their width.These robust characteristics strongly suggest that ReS2 has great potential for applications in optoelectronic nanodevices.

View Article: PubMed Central - PubMed

Affiliation: Institute of High Performance Computing, Singapore 138632, Singapore.

ABSTRACT
Two-dimensional (2D) transition-metal dichalcogenides (TMDs), most notably, MoS2 and WS2, have attracted significant attention due to their sizable and direct bandgap characteristics. Although several interesting MoS2 and WS2-based optoelectronic devices have been reported, their processability and reproducibility are limited since their electrical properties are strongly dependent of the number of layers, strain and sample sizes. It is highly desirable to have a robust direct bandgap TMD, which is insensitive to those factors. In this work, using density functional theory, we explore the effects of layer number, strain and ribbon width on the electronic properties of ReS2, a new member in the TMD family. The calculation results reveal that for monolayer ReS2, the nature (direct versus indirect) and magnitude of its bandgap are insensitive to strain. Importantly, the predicted bandgap and also charge carrier mobilities are nearly independent of the number of layers. In addition, the direct bandgap of ReS2 nanoribbons is only weakly dependent on their width. These robust characteristics strongly suggest that ReS2 has great potential for applications in optoelectronic nanodevices.

No MeSH data available.


Related in: MedlinePlus