Origin of phonon-limited mobility in two-dimensional metal dichalcogenides

2021 ◽  
Vol 34 (1) ◽  
pp. 013003
Author(s):  
Hao Chang ◽  
Hao Wang ◽  
Ke-Ke Song ◽  
Min Zhong ◽  
Li-Bin Shi ◽  
...  
Keyword(s):  
Optical Phonon ◽  
Transport Theory ◽  
Coupling Effect ◽  
Dielectric Constants ◽  
Polar Optical Phonon ◽  
Two Dimensional ◽  
Limited Mobility ◽  
Boltzmann Transport Theory ◽  
2D Semiconductors ◽  
Metal Dichalcogenides

Abstract Metal dichalcogenides are novel two-dimensional (2D) semiconductors after the discovery of graphene. In this article, phonon-limited mobility for six kinds of 2D semiconductors with the composition of MX2 is reviewed, in which M (Cr, Mo and W) is the transition metal, and X (S and Se) is the chalcogen element. The review is divided into three parts. In the first part, we briefly introduce the calculation method of mobility, including the empirical model and Boltzmann transport theory (BTE). The application scope, merits and limitations of these methods are summarized. In the second part, we explore empirical models to calculate the mobility of MX2, including longitudinal acoustic phonon, optical phonon (OP) and polar optical phonon (POP) models. The contribution of multi-valley to mobility is reviewed in the calculation. The differences between static and high-frequency dielectric constants (Δϵ) are only 0.13 and 0.03 for MoS2 and WS2. Such a low value indicates that the polarization hardly changes in the external field. So, their mobility is not determined by POP, but by deformation potential models. Different from GaAs, POP scattering plays a decisive role in its mobility. Our investigations also reveal that the scattering from POP cannot be ignored in CrSe2, MoSe2 and WSe2. In the third parts, we investigate the mobility of MX2 using electron–phonon coupling matrix element, which is based on BTE from the framework of a many-body quantum-field theory. Valence band splitting of MoS2 and WS2 is induced by spin–orbit coupling effect, which leads to the increase of hole mobility. In particular, we review in detail the theoretical and experimental results of MoS2 mobility in recent ten years, and its mobility is also compared with other materials to deepen the understanding.

Strong coupling in two-dimensional materials-based nanostructures: a review

2022 ◽  
Author(s):  
Ye Ming Qing ◽  
Yongze Ren ◽  
Dangyuan Lei ◽  
Hui Feng Ma ◽  
Tie Jun Cui
Keyword(s):  
Strong Coupling ◽  
Coupling Effect ◽  
Transition Metal Dichalcogenides ◽  
Hybrid Nanostructures ◽  
Two Dimensional ◽  
Strong Light ◽  
Two Dimensional Materials ◽  
Potential Applications ◽  
Metal Dichalcogenides ◽  
Emission Behavior

Abstract Strong interaction between electromagnetic radiation and matter leads to the formation of hybrid light-matter states, making the absorption and emission behavior different from those of the uncoupled states. Strong coupling effect results in the famous Rabi splitting and the emergence of new polaritonic eigenmodes, exhibiting spectral anticrossing behavior and unique energy-transfer properties. In recent years, there has been a rapidly increasing number of works focusing on strong coupling between nanostructures and two-dimensional materials (2DMs), because of the exceptional properties and applications they demonstrate. Here, we review the significant recent advances and important developments of strong light-matter interactions in 2DMs-based nanostructures. We adopt the coupled oscillator model to describe the strong coupling and give an overview of various hybrid nanostructures to realize this regime, including graphene-based nanostructures, black phosphorus-based nanostructures, transition-metal dichalcogenides-based nanostructures, etc. In addition, we discuss potential applications that can benefit from these effects and conclude our review with a perspective on the future of this rapidly emerging field.

scholarly journals Bilayer MSe2 (M = Zr, Hf) as promising two-dimensional thermoelectric materials: a first-principles study

RSC Advances ◽  
2019 ◽  
Vol 9 (22) ◽  
pp. 12394-12403 ◽  
Author(s):  
Peng Yan ◽  
Guo-ying Gao ◽  
Guang-qian Ding ◽  
Dan Qin
Keyword(s):  
Thin Films ◽  
Thermoelectric Materials ◽  
First Principles ◽  
Transport Theory ◽  
Two Dimensional ◽  
First Principles Calculations ◽  
Boltzmann Transport ◽  
Thermoelectric Transport ◽  
Boltzmann Transport Theory ◽  
Thermoelectric Transport Properties

Motivated by experimental synthesis of two-dimensional MSe2 (M = Zr, Hf) thin films, we investigate the thermoelectric transport properties of MSe2 (M = Zr, Hf) bilayers by using first-principles calculations and Boltzmann transport theory.

Origin of layer-dependent SERS tunability in 2D transition metal dichalcogenides

2021 ◽  
Author(s):  
Mingze Li ◽  
Yimeng Gao ◽  
Xingce Fan ◽  
Yunjia Wei ◽  
Qi Hao ◽  
...  
Keyword(s):  
Transition Metal ◽  
Noble Metals ◽  
Transition Metal Dichalcogenides ◽  
Two Dimensional ◽  
2D Semiconductors ◽  
Surface Enhanced ◽  
The Matrix ◽  
Surface Enhanced Raman ◽  
Metal Dichalcogenides ◽  
Enhanced Raman Scattering

Two-dimensional (2D) semiconductors are expected to replace noble metals to become the matrix materials of next generation of commercial surface-enhanced Raman scattering (SERS) chips. Herein, we systematically studied the influence...

scholarly journals Optical activity in chiral stacks of 2D semiconductors

Nanophotonics ◽  
2018 ◽  
Vol 7 (4) ◽  
pp. 753-762 ◽  
Author(s):  
Alexander V. Poshakinskiy ◽  
Dmitrii R. Kazanov ◽  
Tatiana V. Shubina ◽  
Sergey A. Tarasenko
Keyword(s):  
Optical Activity ◽  
Transition Metal Dichalcogenides ◽  
Microscopic Theory ◽  
Interlayer Coupling ◽  
Two Dimensional ◽  
Circularly Polarized ◽  
Semiconductor Crystals ◽  
2D Semiconductors ◽  
Metal Dichalcogenides ◽  
Dark Exciton

AbstractWe show that the stacks of two-dimensional semiconductor crystals with the chiral packing exhibit optical activity and circular dichroism. We develop a microscopic theory of these phenomena in the spectral range of exciton transitions that takes into account the spin-dependent hopping of excitons between the layers in the stack and the interlayer coupling of excitons via electromagnetic field. For the stacks of realistic two-dimensional semiconductors such as transition metal dichalcogenides, we calculate the rotation and ellipticity angles of radiation transmitted through such structures. The angles are resonantly enhanced at the frequencies of both bright and dark exciton modes in the stack. We also study the photoluminescence of chiral stacks and show that it is circularly polarized.

scholarly journals Modulation of photocarrier relaxation dynamics in two-dimensional semiconductors

2020 ◽  
Vol 9 (1) ◽  
Author(s):  
Yuhan Wang ◽  
Zhonghui Nie ◽  
Fengqiu Wang
Keyword(s):  
Electric Fields ◽  
Mechanical Strain ◽  
Transition Metal Dichalcogenides ◽  
Binding Energies ◽  
Two Dimensional ◽  
Coulomb Interactions ◽  
Relaxation Dynamics ◽  
Strong Light ◽  
2D Semiconductors ◽  
Metal Dichalcogenides

AbstractDue to strong Coulomb interactions, two-dimensional (2D) semiconductors can support excitons with large binding energies and complex many-particle states. Their strong light-matter coupling and emerging excitonic phenomena make them potential candidates for next-generation optoelectronic and valleytronic devices. The relaxation dynamics of optically excited states are a key ingredient of excitonic physics and directly impact the quantum efficiency and operating bandwidth of most photonic devices. Here, we summarize recent efforts in probing and modulating the photocarrier relaxation dynamics in 2D semiconductors. We classify these results according to the relaxation pathways or mechanisms they are associated with. The approaches discussed include both tailoring sample properties, such as the defect distribution and band structure, and applying external stimuli such as electric fields and mechanical strain. Particular emphasis is placed on discussing how the unique features of 2D semiconductors, including enhanced Coulomb interactions, sensitivity to the surrounding environment, flexible van der Waals (vdW) heterostructure construction, and non-degenerate valley/spin index of 2D transition metal dichalcogenides (TMDs), manifest themselves during photocarrier relaxation and how they can be manipulated. The extensive physical mechanisms that can be used to modulate photocarrier relaxation dynamics are instrumental for understanding and utilizing excitonic states in 2D semiconductors.

scholarly journals Weak ferroelectric charge transfer in layer-asymmetric bilayers of 2D semiconductors

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Fábio Ferreira ◽  
Vladimir V. Enaldiev ◽  
Vladimir I. Fal’ko ◽  
Samuel J. Magorrian
Keyword(s):  
Charge Transfer ◽  
Transition Metal ◽  
Transition Metal Dichalcogenides ◽  
Potential Difference ◽  
Inversion Symmetry ◽  
Two Dimensional ◽  
2D Semiconductors ◽  
Metal Dichalcogenides

AbstractIn bilayers of two-dimensional semiconductors with stacking arrangements which lack inversion symmetry charge transfer between the layers due to layer-asymmetric interband hybridisation can generate a potential difference between the layers. We analyse bilayers of transition metal dichalcogenides (TMDs)—in particular, $$\hbox {WSe}_2$$ WSe 2 —for which we find a substantial stacking-dependent charge transfer, and InSe, for which the charge transfer is found to be negligibly small. The information obtained about TMDs is then used to map potentials generated by the interlayer charge transfer across the moiré superlattice in twistronic bilayers.

Analytical Theory of Electron Mobility and Drift Velocity in GaN

1996 ◽  
Vol 449 ◽  
Author(s):  
B. L. Gelmont ◽  
M. S. Shur ◽  
M. Stroscio
Keyword(s):  
Electric Fields ◽  
Drift Velocity ◽  
Optical Phonon ◽  
Electron Mobility ◽  
Phonon Scattering ◽  
Electron Gas ◽  
Transport Equations ◽  
Polar Optical Phonon ◽  
Two Dimensional ◽  
Optical Phonon Scattering

ABSTRACTWe derive balance transport equations for the electron mobility and drift velocity, which are applicable at any degeneracy of the electron gas. These equations account for the polar optical phonon scattering and ionized impurity scattering and include the effects of screening. These equations are valid only for very high concentrations (above 1019 cm-3 for GaN). However, the comparison with the results of Monte Carlo simulations shows that they fairly accurately reproduce the field-velocity curves in GaN in moderate electric fields (up to 100 kV/cm). The comparison with the electron mobility calculated using the two-step model [1] shows a much larger difference but allows us to illustrate the trends in mobility dependencies caused by electron-electron collisions. We also derive the balance transport equations accounting for the polar optical phonon scattering in a two-dimensional electron gas. The calculations based on these equations, show that the unscreened polar optical scattering mobility is smaller in the two-dimensional gas than in the bulk intrinsic semiconductor and that the mobility decreases with the decrease of the quantum well thickness.

scholarly journals Promising Thermoelectric Performance in Two-Dimensional Semiconducting Boron Monolayer

2021 ◽  
Vol 9 ◽  
Author(s):  
Yonglan Hu ◽  
Ding Li ◽  
Rongkun Liu ◽  
Shichang Li ◽  
Chunbao Feng ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Lattice Thermal Conductivity ◽  
Transport Theory ◽  
Thermoelectric Performance ◽  
Two Dimensional ◽  
Boltzmann Transport ◽  
Hole Effective Mass ◽  
Boltzmann Transport Theory ◽  
Special Character ◽  
Type Power

A heavy element is a special character for high thermoelectric performance since it generally guarantees a low lattice thermal conductivity. Here, we unexpectedly found a promising thermoelectric performance in a two-dimensional semiconducting monolayer consisting of a light boron element. Using first-principles combined with the Boltzmann transport theory, we have shown that in contrast to graphene or black phosphorus, the boron monolayer has a low lattice thermal conductivity arising from its complex crystal of hexagonal vacancies. The conduction band with an intrinsic camelback shape leads to the high DOS and a high n-type Seebeck coefficient, while the highly degenerate valence band along with the small hole effective mass contributes to the high p-type power factor. As a result, we obtained the p-type thermoelectric figure of merit up to 0.96 at 300 K, indicating that the boron monolayer is a promising p-type thermoelectric material.

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