Multi-terminal transport measurements of MoS2 using a van der Waals heterostructure device platform

Abstract

Atomically thin two-dimensional semiconductors such as MoS 2 hold great promise in electrical, optical, and mechanical devices and display novel physical phenomena. However, the electron mobility of mono-and few-layer MoS 2 has so far been substantially below theoretically predicted limits, which has hampered efforts to observe its intrinsic quantum transport behaviours. Potential sources of disorder and scattering include both defects such as sulfur vacancies in the MoS 2 itself, and extrinsic sources such as charged impurities and remote optical phonons from oxide dielectrics. To reduce extrinsic scattering, here we developed a van der Waals heterostructure device platform where MoS 2 layers are fully encapsulated within hexagonal boron nitride, and electrically contacted in a multi-terminal geometry using gate-tunable graphene electrodes. Magneto-transport measurements show dramatic improvements in performance, including a record-high Hall mobility reaching 34,000 cm 2 /Vs for 6-layer MoS 2 at low temperature, confirming that low-temperature performance in previous studies was limited by extrinsic interfacial impurities rather than bulk defects in the MoS 2 . We also observed Shubnikov-de Haas oscillations for the first time in high-mobility monolayer and few-layer MoS 2 . Modeling of potential scattering sources and quantum lifetime analysis indicate that a combination of short-ranged and long-ranged interfacial scattering limits low-temperature mobility of MoS 2 . 3Following the many advances in basic science and applications of graphene, other twodimensional (2D) materials, especially transition metal dichalcogenides (TMDCs), have attracted significant interest for their fascinating electrical, optical, and mechanical properties [1][2][3][4][5][6][7][8] . Among the TMDCs, semiconducting MoS 2 has been the mostly widely studied: it shows a thicknessdependent electronic band structure 3,5 , reasonably high carrier mobility 1,2,6-9 , and novel phenomena such as coupled spin-valley physics and the valley Hall effect 10-14 , leading to various applications, such as transistors 1,7,15 , memories 16 , logic circuits 17,18 , light-emitters 19 , and photo-detectors 20 with flexibility and transparency 2,21 . However, as for any 2D material, the electrical and optical properties of MoS 2 are strongly affected by impurities and its dielectric environment 1,2,9,22 , hindering the study of intrinsic physics and limiting the design of 2D-material-based devices. In particular, the theoretical upper bound of the electron mobility of monolayer (1L) MoS 2 is predicted to be from several tens to a few thousands at room temperature (T) and exceed 10 5 cm 2 /Vs at low T depending on the dielectric environment, impurity density and charge carrier density [23][24][25] . In contrast, experimentally measured 1L MoS 2 devices on SiO 2 substrates have exhibited room-T two-terminal field-effect mobility that ranges from 0.1 -55 cm 2 /Vs 1,26,27 . This value increases to 15 -60 cm 2 /Vs with encapsulation by highdielectric materials 1...

Low-Frequency Electronic Noise in Quasi-1D TaSe3 van der Waals Nanowires

“…The investigations of the two-dimensional layers and heterostructures revealed new physics and demonstrated promising applications [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Starting with graphene [3][4][5], and spreading to a wide range of layered van der Waals materials [6][7][8][9][10], successful isolation of individual atomic layers from their respective bulk crystals by mechanical exfoliation led to the fast growing research activities in the 2D materials.…”

Linear magnetotransport in monolayerMoS2

“…Only recently, the SdHO was observed experimentally for the first time in monolayer and few-layer MoS 2 . 23 In this paper, we apply a momentum balance equation to investigate the linear magnetotransport at both low and high temperatures including SdHO and magnetophonon resonance (MPR) effect induced by optical and acoustic phonons for both suspended and nonsuspended samples.…”

Negative compressibility in graphene-terminated black phosphorus heterostructures

“…The effects of negative compressibility have been previously observed in ultraclean systems, such as in high-quality LaAlO 3 /SrTiO 3 interfaces [9], two-dimensional (2D) GaAs systems [4,[10][11][12], and ferroelectric materials [13], where Coulomb interactions are normally strong and play an important role in transport properties. Newly emerged 2D layered semiconductors, such as transition-metal dichalcogenides [14][15][16][17][18] and black phosphorus (BP) [19][20][21][22][23][24][25][26][27][28], are new platforms for both nanotechnology and fundamental physics. Among these 2D materials, atomically thin BP is a promising channel material of FETs with high mobility [24][25][26][27] and high stability by encapsulating BP with hexagonal boron nitride (BN) sheets.…”