scholarly journals Direct observation of valley-coupled topological current in MoS2

2019 ◽  
Vol 5 (4) ◽  
pp. eaau6478 ◽  
Author(s):  
Terry Y. T. Hung ◽  
Kerem Y. Camsari ◽  
Shengjiao Zhang ◽  
Pramey Upadhyaya ◽  
Zhihong Chen
Keyword(s):  
Hall Effect ◽  
Room Temperature ◽  
Electronic Devices ◽  
Transition Metal Dichalcogenides ◽  
Channel Length ◽  
Degree Of Freedom ◽  
Topological Current ◽  
Metal Dichalcogenides ◽  
New Generation ◽  
Valley Hall Effect

The valley degree of freedom of electrons in two-dimensional transition metal dichalcogenides has been extensively studied by theory (1–4), optical (5–9), and optoelectronic (10–13) experiments. However, generation and detection of pure valley current without relying on optical selection have not yet been demonstrated in these materials. Here, we report that valley current can be electrically induced and detected through the valley Hall effect and inverse valley Hall effect, respectively, in monolayer molybdenum disulfide. We compare temperature and channel length dependence of nonlocal electrical signals in monolayer and multilayer samples to distinguish the valley Hall effect from classical ohmic contributions. Notably, valley transport is observed over a distance of 4 μm in monolayer samples at room temperature. Our findings will enable a new generation of electronic devices using the valley degree of freedom, which can be used for future novel valleytronic applications.

scholarly journals Microscopic Origin of the Valley Hall Effect in Transition Metal Dichalcogenides Revealed by Wavelength-Dependent Mapping

Nano Letters ◽  
2017 ◽  
Vol 17 (9) ◽  
pp. 5719-5725 ◽  
Author(s):  
Nicolas Ubrig ◽  
Sanghyun Jo ◽  
Marc Philippi ◽  
Davide Costanzo ◽  
Helmuth Berger ◽  
...  
Keyword(s):  
Transition Metal ◽  
Hall Effect ◽  
Transition Metal Dichalcogenides ◽  
Metal Dichalcogenides ◽  
Valley Hall Effect ◽  
Microscopic Origin

scholarly journals Valley-Selective Response of Nanostructures Coupled to 2D Transition-Metal Dichalcogenides

2018 ◽  
Vol 8 (7) ◽  
pp. 1157 ◽  
Author(s):  
Alexander Krasnok ◽  
Andrea Alù
Keyword(s):  
Transition Metal ◽  
Room Temperature ◽  
State Of The Art ◽  
Transition Metal Dichalcogenides ◽  
Zone Boundary ◽  
Brillouin Zone Boundary ◽  
Directional Emission ◽  
Metal Dichalcogenides ◽  
On Chip ◽  
Valley Hall Effect

Monolayer (1L) transition-metal dichalcogenides (TMDCs) are attractive materials for several optoelectronic applications because of their strong excitonic resonances and valley-selective response. Valley excitons in 1L-TMDCs are formed at opposite points of the Brillouin zone boundary, giving rise to a valley degree of freedom that can be treated as a pseudospin, and may be used as a platform for information transport and processing. However, short valley depolarization times and relatively short exciton lifetimes at room temperature prevent using valley pseudospins in on-chip integrated valley devices. Recently, it was demonstrated how coupling these materials to optical nanoantennas and metasurfaces can overcome this obstacle. Here, we review the state-of-the-art advances in valley-selective directional emission and exciton sorting in 1L-TMDC mediated by nanostructures and nanoantennas. We briefly discuss the optical properties of 1L-TMDCs paying special attention to their photoluminescence/absorption spectra, dynamics of valley depolarization, and the valley Hall effect. Then, we review recent works on nanostructures for valley-selective directional emission from 1L-TMDCs.

scholarly journals Optoelectronics with single layer group-VIB transition metal dichalcogenides

Nanophotonics ◽  
2018 ◽  
Vol 7 (10) ◽  
pp. 1589-1600 ◽  
Author(s):  
M.A. Khan ◽  
Michael N. Leuenberger
Keyword(s):  
Transition Metal ◽  
Electronic Devices ◽  
Transition Metal Dichalcogenides ◽  
Single Layer ◽  
Spin Orbit Coupling ◽  
Electroluminescent Devices ◽  
Metal Dichalcogenides ◽  
Fundamental Research ◽  
Excitonic Effects ◽  
Strong Spin

AbstractThe discovery of two-dimensional (2D) materials has opened up new frontiers and challenges for exploring fundamental research. Recently, single-layer (SL) transition metal dichalcogenides (TMDCs) have emerged as candidate materials for electronic and optoelectronic applications. In contrast to graphene, SL TMDCs have sizable band gaps that change from indirect to direct in SLs, which is useful in making thinner and more efficient electronic devices, such as transistors, photodetectors, and electroluminescent devices. In addition, SL TMDCs show strong spin-orbit coupling effects at the valence band edges, giving rise to the observation of valley-selective optical excitations. Here, we review the basic electronic and optical properties of pure and defected group-VIB SL TMDCs, with emphasis on the strong excitonic effects and their prospect for future optoelectronic devices.

Mechanisms of negative differential resistance in glutamine-functionalized WS2 quantum dots

2021 ◽  
Author(s):  
Denice Feria ◽  
Sonia Sharma ◽  
Yu-Ting Chen ◽  
Zhi-Ying Weng ◽  
Kuo-Pin Chiu ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Negative Differential Resistance ◽  
Electronic Devices ◽  
Transition Metal Dichalcogenides ◽  
Differential Resistance ◽  
Voltage Range ◽  
Current Voltage ◽  
Metal Dichalcogenides ◽  
Current Voltage Characteristics ◽  
Memory Applications

Abstract Understanding the mechanism of the negative differential resistance (NDR) in transition metal dichalcogenides is essential for fundamental science and the development of electronic devices. Here, the NDR of the current-voltage characteristics was observed based on the glutamine-functionalized WS2 quantum dots (QDs). The NDR effect can be adjusted by varying the applied voltage range, air pressure, surrounding gases, and relative humidity. A peak-to-valley current ratio as high as 6.3 has been achieved at room temperature. Carrier trapping induced by water molecules was suggested to be responsible for the mechanism of the NDR in the glutamine-functionalized WS2 QDs. Investigating the NDR of WS2 QDs may promote the development of memory applications and emerging devices.

Design, simulation and optimization of multi-layered MoS2 based FET devices

2021 ◽  
Author(s):  
Agraj Khare ◽  
Priyanka Dwivedi
Keyword(s):  
Dynamic Range ◽  
Field Effect Transistors ◽  
Electronic Devices ◽  
Transition Metal Dichalcogenides ◽  
Wave Model ◽  
Threshold Potential ◽  
Simulation And Optimization ◽  
Full Wave ◽  
Emerging Trends ◽  
Metal Dichalcogenides

Abstract Transition-metal Dichalcogenides (TMDs) materials are getting attention in the emerging trends of electronic devices development for a variety of applications. One of such materials is MoS2 which is best suited for developing deeply scaled field effect transistors (FETs). With the plethora of TMDs available, MoS2 is the most widely studied and used material because of its tunable properties like band gap, morphology, optical, structural, electrical, flexible etc. This paper represents the design and simulation aspect of the multi-layered MoS2 Based FET devices. Evidence of change in comparative electrical characteristics of MoS2 based FET devices due to variation of thickness and doping of the gate layer are also presented. In this contribution, we have simulated a full-wave model using the COMSOL Multiphysics module for two different thicknesses 0.7 nm and 1 nm. The FET device with 1 nm MoS2 offers a better dynamic range of operation and has a broader spectrum of threshold potential. The characteristic plots of the 1 nm device showed very less deviation from ideal trends than in the 0.7 nm device. The optimized FET structure offers better performance and efficiency in terms of electrical properties.

Theoretical characterization of the electronic properties of heterogeneous vertical stacks of 2D metal dichalcogenides containing one doped layer

2020 ◽  
Vol 22 (25) ◽  
pp. 14088-14098
Author(s):  
Amine Slassi ◽  
David Cornil ◽  
Jérôme Cornil
Keyword(s):  
Transition Metal ◽  
Electronic Properties ◽  
Van Der Waals ◽  
Transition Metal Dichalcogenides ◽  
Optoelectronic Devices ◽  
Metal Dichalcogenides ◽  
Theoretical Characterization ◽  
New Generation

The rise of van der Waals hetero-structures based on transition metal dichalcogenides (TMDs) opens the door to a new generation of optoelectronic devices.

scholarly journals A Horizontal-Gate Monolayer MoS2 Transistor Based on Image Force Barrier Reduction

Nanomaterials ◽  
2019 ◽  
Vol 9 (9) ◽  
pp. 1245 ◽  
Author(s):  
Kun Yang ◽  
Hongxia Liu ◽  
Shulong Wang ◽  
Wei Li ◽  
Tao Han
Keyword(s):  
Carrier Mobility ◽  
Transition Metal Dichalcogenides ◽  
Image Force ◽  
Drain Current ◽  
Equivalent Model ◽  
Two Dimensional ◽  
Monolayer Mos2 ◽  
Two Dimensional Materials ◽  
Metal Dichalcogenides ◽  
New Generation

Transition metal dichalcogenides (TMDCs) have received wide attention as a new generation of semiconductor materials. However, there are still many problems to be solved, such as low carrier mobility, contact characteristics between metal and two-dimensional materials, and complicated fabrication processes. In order to overcome these problems, a large amount of research has been carried out so that the performance of the device has been greatly improved. However, most of these studies are based on complicated fabrication processes which are not conducive to the improvement of integration. In view of this problem, a horizontal-gate monolayer MoS2 transistor based on image force barrier reduction is proposed, in which the gate is in the same plane as the source and drain and comparable to back-gated transistors on-off ratios up to 1 × 104 have been obtained. Subsequently, by combining the Y-Function method (YFM) and the proposed diode equivalent model, it is verified that Schottky barrier height reduction is the main reason giving rise to the observed source-drain current variations. The proposed structure of the device not only provides a new idea for the high integration of two-dimensional devices, but also provides some help for the study of contact characteristics between two-dimensional materials and metals.

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