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

The evolution of the band structure of the WS2/MoSe2/WS2 quantum wells with increased MoSe2 thickness from (a) n = 1 to (d) n = 4.Inset in (a) shows the rectangular Brillouin zone of WS2/MoSe2/WS2 quantum wells. The arrows show the change of CBM at the A-point and VBM at the Γ-point; the dashed horizontal lines represent the Fermi level.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f3: The evolution of the band structure of the WS2/MoSe2/WS2 quantum wells with increased MoSe2 thickness from (a) n = 1 to (d) n = 4.Inset in (a) shows the rectangular Brillouin zone of WS2/MoSe2/WS2 quantum wells. The arrows show the change of CBM at the A-point and VBM at the Γ-point; the dashed horizontal lines represent the Fermi level.

Mentions: Figure 3 shows the evolution of band structure of WS2/MoSe2/WS2 quantum well with the thickness of MoSe2 varying from n = 1 to 4. The band gap locates at the A-point and almost linearly decreases with the increasing of MoSe2 thickness, as indicated in Fig. 1(b). In Fig. 3, the arrows represent the change of VBM position at the Γ-point and CBM position at the A-point. As MoSe2 thickness increases, both VBM at the Γ-point and CBM at the A-point shift downward; mini-bands tend to form at the bottom of conduction band. At the Γ-point, a gradual increase of an energy level can be traced in the band structures. It can be reasonably extrapolated that this energy level will further increase as the MoSe2 thickness increases, and a direct-indirect band gap crossover can be foreseen when the MoSe2 thickness is beyond a critical value. It should be pointed out that the band gap of the WS2/MoSe2/WS2 quantum well will probably approach to a constant value (on the basis of band alignment of WS2 and MoSe2) when the thickness of MoSe2 is sufficiently large. As the thickness of MoSe2 increases within a limitation, the electric field becomes stronger and the gap nature can be continuously tuned4142. Figure 1(c) indicates the binding energy of forming the quantum well, defined as the energy difference between the quantum well and the constituent TMDs. The binding energies of WS2/MoSe2/WS2 quantum wells are fairly negative, revealing the formation of covalent bonds, and rapidly to be convergent due to the effective screening of the interface interactions as the MoSe2 thickness increases.


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)

The evolution of the band structure of the WS2/MoSe2/WS2 quantum wells with increased MoSe2 thickness from (a) n = 1 to (d) n = 4.Inset in (a) shows the rectangular Brillouin zone of WS2/MoSe2/WS2 quantum wells. The arrows show the change of CBM at the A-point and VBM at the Γ-point; the dashed horizontal lines represent the Fermi level.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f3: The evolution of the band structure of the WS2/MoSe2/WS2 quantum wells with increased MoSe2 thickness from (a) n = 1 to (d) n = 4.Inset in (a) shows the rectangular Brillouin zone of WS2/MoSe2/WS2 quantum wells. The arrows show the change of CBM at the A-point and VBM at the Γ-point; the dashed horizontal lines represent the Fermi level.
Mentions: Figure 3 shows the evolution of band structure of WS2/MoSe2/WS2 quantum well with the thickness of MoSe2 varying from n = 1 to 4. The band gap locates at the A-point and almost linearly decreases with the increasing of MoSe2 thickness, as indicated in Fig. 1(b). In Fig. 3, the arrows represent the change of VBM position at the Γ-point and CBM position at the A-point. As MoSe2 thickness increases, both VBM at the Γ-point and CBM at the A-point shift downward; mini-bands tend to form at the bottom of conduction band. At the Γ-point, a gradual increase of an energy level can be traced in the band structures. It can be reasonably extrapolated that this energy level will further increase as the MoSe2 thickness increases, and a direct-indirect band gap crossover can be foreseen when the MoSe2 thickness is beyond a critical value. It should be pointed out that the band gap of the WS2/MoSe2/WS2 quantum well will probably approach to a constant value (on the basis of band alignment of WS2 and MoSe2) when the thickness of MoSe2 is sufficiently large. As the thickness of MoSe2 increases within a limitation, the electric field becomes stronger and the gap nature can be continuously tuned4142. Figure 1(c) indicates the binding energy of forming the quantum well, defined as the energy difference between the quantum well and the constituent TMDs. The binding energies of WS2/MoSe2/WS2 quantum wells are fairly negative, revealing the formation of covalent bonds, and rapidly to be convergent due to the effective screening of the interface interactions as the MoSe2 thickness increases.

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