Limits...
Controlling the Electronic Structures and Properties of in-Plane Transition-Metal Dichalcogenides Quantum Wells.

Wei W, Dai Y, Niu C, Huang B - Sci Rep (2015)

Bottom Line: The true type-II alignment forms due to the coherent lattice and strong interface coupling suggesting the effective separation and collection of excitons.The intrinsic electric polarization enhances the spin-orbital coupling and demonstrates the possibility to achieve topological insulator state and valleytronics in TMD quantum wells.In-plane TMD quantum wells have opened up new possibilities of applications in next-generation devices at nanoscale.

View Article: PubMed Central - PubMed

Affiliation: School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China.

ABSTRACT
In-plane transition-metal dichalcogenides (TMDs) quantum wells have been studied on the basis of first-principles density functional calculations to reveal how to control the electronic structures and the properties. In collection of quantum confinement, strain and intrinsic electric field, TMD quantum wells offer a diverse of exciting new physics. The band gap can be continuously reduced ascribed to the potential drop over the embedded TMD and the strain substantially affects the band gap nature. The true type-II alignment forms due to the coherent lattice and strong interface coupling suggesting the effective separation and collection of excitons. Interestingly, two-dimensional quantum wells of in-plane TMD can enrich the photoluminescence properties of TMD materials. The intrinsic electric polarization enhances the spin-orbital coupling and demonstrates the possibility to achieve topological insulator state and valleytronics in TMD quantum wells. In-plane TMD quantum wells have opened up new possibilities of applications in next-generation devices at nanoscale.

No MeSH data available.


Related in: MedlinePlus

Atomic model representing the TMD quantum wells, the small spheres are non-metal atoms (S, Se and Te), while big spheres are metal atoms (Mo and W); (a) side and (b) top views of WS2/MoSe2/WS2 quantum well with the thickness of MoSe2 n being 4 (n corresponds to the number of MoSe2 units in the unit cell of quantum well); in (b) the rectangle represent a unit cell of the quantum well. The (c) band gap and (d) binding energy of WS2/MoSe2/WS2 quantum well as a function of the MoSe2 thickness. The binding energy is calculated by subtracting the total energies of WS2 and MoSe2 from the total energy of the WS2/MoSe2/WS2 quantum well, defined as Eb = E(WS2/MoSe2/WS2)-E(WS2)-E(MoSe2).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4663467&req=5

f1: Atomic model representing the TMD quantum wells, the small spheres are non-metal atoms (S, Se and Te), while big spheres are metal atoms (Mo and W); (a) side and (b) top views of WS2/MoSe2/WS2 quantum well with the thickness of MoSe2 n being 4 (n corresponds to the number of MoSe2 units in the unit cell of quantum well); in (b) the rectangle represent a unit cell of the quantum well. The (c) band gap and (d) binding energy of WS2/MoSe2/WS2 quantum well as a function of the MoSe2 thickness. The binding energy is calculated by subtracting the total energies of WS2 and MoSe2 from the total energy of the WS2/MoSe2/WS2 quantum well, defined as Eb = E(WS2/MoSe2/WS2)-E(WS2)-E(MoSe2).

Mentions: In this work, we constructed a rectangular unit cell for the calculations, as shown in Fig. 1(a,b). In this model, dimension in a direction is infinite due to the periodic bound condition, while in b direction the length is around 70 Å. As a consequence, the band structures should be calculated in a two-dimensional rectangular Brillouin zone; however, we confirm that the band dispersion relation normal to the zigzag interfaces completely reflects the decisive characters of the band structures and we show the band structures in Γ-X direction. Although the experiments suggested in-plane TMD heterointerfaces in triangular shape with three-fold symmetry, interfacing is along the zigzag direction1011121314 and this asymmetric nature is not necessary to consider in our calculations. It should be pointed out that the zigzag direction of interfacing in TMD quantum wells corresponds to the Γ-K direction of the two-dimensional hexagonal Brillouin zone, as indicated in Fig. 2(a). In consideration of band folding, the K-point of the hexagonal Brillouin zone is folded to the A-point of the rectangular Brillouin zone. In other words, that is why the VBM at Γ- and A-point manifests strong sensitivity to the interaction of constituent TMDs, as found in TMD heterobilayers222327.


Controlling the Electronic Structures and Properties of in-Plane Transition-Metal Dichalcogenides Quantum Wells.

Wei W, Dai Y, Niu C, Huang B - Sci Rep (2015)

Atomic model representing the TMD quantum wells, the small spheres are non-metal atoms (S, Se and Te), while big spheres are metal atoms (Mo and W); (a) side and (b) top views of WS2/MoSe2/WS2 quantum well with the thickness of MoSe2 n being 4 (n corresponds to the number of MoSe2 units in the unit cell of quantum well); in (b) the rectangle represent a unit cell of the quantum well. The (c) band gap and (d) binding energy of WS2/MoSe2/WS2 quantum well as a function of the MoSe2 thickness. The binding energy is calculated by subtracting the total energies of WS2 and MoSe2 from the total energy of the WS2/MoSe2/WS2 quantum well, defined as Eb = E(WS2/MoSe2/WS2)-E(WS2)-E(MoSe2).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4663467&req=5

f1: Atomic model representing the TMD quantum wells, the small spheres are non-metal atoms (S, Se and Te), while big spheres are metal atoms (Mo and W); (a) side and (b) top views of WS2/MoSe2/WS2 quantum well with the thickness of MoSe2 n being 4 (n corresponds to the number of MoSe2 units in the unit cell of quantum well); in (b) the rectangle represent a unit cell of the quantum well. The (c) band gap and (d) binding energy of WS2/MoSe2/WS2 quantum well as a function of the MoSe2 thickness. The binding energy is calculated by subtracting the total energies of WS2 and MoSe2 from the total energy of the WS2/MoSe2/WS2 quantum well, defined as Eb = E(WS2/MoSe2/WS2)-E(WS2)-E(MoSe2).
Mentions: In this work, we constructed a rectangular unit cell for the calculations, as shown in Fig. 1(a,b). In this model, dimension in a direction is infinite due to the periodic bound condition, while in b direction the length is around 70 Å. As a consequence, the band structures should be calculated in a two-dimensional rectangular Brillouin zone; however, we confirm that the band dispersion relation normal to the zigzag interfaces completely reflects the decisive characters of the band structures and we show the band structures in Γ-X direction. Although the experiments suggested in-plane TMD heterointerfaces in triangular shape with three-fold symmetry, interfacing is along the zigzag direction1011121314 and this asymmetric nature is not necessary to consider in our calculations. It should be pointed out that the zigzag direction of interfacing in TMD quantum wells corresponds to the Γ-K direction of the two-dimensional hexagonal Brillouin zone, as indicated in Fig. 2(a). In consideration of band folding, the K-point of the hexagonal Brillouin zone is folded to the A-point of the rectangular Brillouin zone. In other words, that is why the VBM at Γ- and A-point manifests strong sensitivity to the interaction of constituent TMDs, as found in TMD heterobilayers222327.

Bottom Line: The true type-II alignment forms due to the coherent lattice and strong interface coupling suggesting the effective separation and collection of excitons.The intrinsic electric polarization enhances the spin-orbital coupling and demonstrates the possibility to achieve topological insulator state and valleytronics in TMD quantum wells.In-plane TMD quantum wells have opened up new possibilities of applications in next-generation devices at nanoscale.

View Article: PubMed Central - PubMed

Affiliation: School of Physics, State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China.

ABSTRACT
In-plane transition-metal dichalcogenides (TMDs) quantum wells have been studied on the basis of first-principles density functional calculations to reveal how to control the electronic structures and the properties. In collection of quantum confinement, strain and intrinsic electric field, TMD quantum wells offer a diverse of exciting new physics. The band gap can be continuously reduced ascribed to the potential drop over the embedded TMD and the strain substantially affects the band gap nature. The true type-II alignment forms due to the coherent lattice and strong interface coupling suggesting the effective separation and collection of excitons. Interestingly, two-dimensional quantum wells of in-plane TMD can enrich the photoluminescence properties of TMD materials. The intrinsic electric polarization enhances the spin-orbital coupling and demonstrates the possibility to achieve topological insulator state and valleytronics in TMD quantum wells. In-plane TMD quantum wells have opened up new possibilities of applications in next-generation devices at nanoscale.

No MeSH data available.


Related in: MedlinePlus