Universal low-temperature Ohmic contacts for quantum transport in transition metal dichalcogenides

Abstract

Low carrier mobility and high electrical contact resistance are two major obstacles prohibiting explorations of quantum transport in TMDCs. Here, we demonstrate an effective method to establish low-temperature Ohmic contacts in boron nitride encapsulated TMDC devices based on selective etching and conventional electron-beam evaporation of metal electrodes. This method works for most extensively studied TMDCs in recent years, including MoS2, MoSe2, WSe2, WS2, and 2H-MoTe2. Low electrical contact resistance is achieved at 2 K. All of the few-layer TMDC devices studied show excellent performance with remarkably improved field-effect mobilities ranging from 2300 cm2/V s to 16000 cm2/V s, as verified by the high carrier mobilities extracted from Hall effect measurements. Moreover, both high-mobility n-type and p-type TMDC channels can be realized by simply using appropriate contact metals. Prominent Shubnikov-de Haas oscillations have been observed and investigated in these high-quality TMDC devices.

The methods have been applied to p-type WSe2 and other TMDC based devices. Supplementary information is included

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• Intrinsic valley Hall transport in atomically thin MoS2
• One-dimensional edge contacts to a monolayer semiconductor
• Observation of Valley Zeeman and Quantum Hall Effects at Q Valley of Few-Layer Transition Metal Disulfides
• Charge-transfer Contact to a High-Mobility Monolayer Semiconductor
• Tuning Rashba Spin-Orbit Coupling in Gated Multilayer InSe
• Steady states and edge state transport in topological Floquet-Bloch systems
• Effects of Hexagonal Boron Nitride Encapsulation on the Electronic Structure of Few-layer MoS${}_2$
• Odd-integer quantum Hall states and giant spin susceptibility in p-type few-layer WSe2
• High-performance monolayer MoS2 field-effect transistor with large-scale nitrogen-doped graphene electrodes for Ohmic contact
• Quantum Transport in Two-Dimensional WS${}_2$ with High-Efficiency Carrier Injection Through Indium Alloy Contacts
• Probing Landau levels of strongly interacting massive Dirac electrons in layer-polarized MoS${}_2$
• Landau-quantized excitonic absorption and luminescence in a monolayer valley semiconductor
• Tunable $\Gamma -K$ Valley Populations in Hole-Doped Trilayer WSe${}_2$
• Spin accumulation and dynamics in inversion-symmetric van der Waals crystals
• Topography preserved microwave plasma etching for top-down layer engineering in MoS2 and other van der Waals materials
• Low-Temperature 2D/2D Ohmic Contacts in WSe${}_2$ Field-Effect Transistors as a Platform for the 2D Metal-Insulator Transition
• Weak localization in boron nitride encapsulated bilayer MoS${}_2$
• Clean BN encapsulated 2D FETs with lithography compatible contacts
• Quantum time-dependent Monte Carlo simulation of electron devices with 2D linear-band materials: a genuine TeraHertz signature for graphene
• Quantum oscillations in 2D electron gases with spin-orbit and Zeeman interactions
• Intrinsic Electronic Properties of BN Encapsulated, van der Waals Contacted MoSe${}_2$ FETs
• Density-dependent spin susceptibility and effective mass in monolayer MoSe2