Hysteresis-Free High Mobility Graphene Encapsulated in Tungsten Disulfide

Abstract

High mobility is a crucial requirement for a large variety of electronic device applications. The state-of-the-art for high quality graphene devices is based on heterostructures made with graphene encapsulated in $>80$nm-thick flakes of hexagonal boron nitride (hBN). Unfortunately, scaling up multilayer hBN while precisely controlling the number of layers remains an elusive challenge, resulting in a rough material unable to enhance the mobility of graphene. This leads to the pursuit of alternative, scalable materials, which can be simultaneously used as substrate and encapsulant for graphene. Tungsten disulfide (WS${}_2$) is a transition metal dichalcogenide, which was successfully grown in large ($\sim$mm-size) multi-layers by chemical vapour deposition. However, the resistance \textit{vs} gate voltage characteristics when gating graphene through WS${}_2$ exhibit largely hysteretic shifts of the charge neutrality point (CNP) in the order of $\Delta n\sim$2.6$\cdot$10${}^{11}$ cm${}^{-2}$, hindering the use of WS${}_2$ as a reliable encapsulant. The hysteresis originates due to the charge traps from sulfur vacancies present in WS${}_2$. In this work, we report for the first time the use of WS${}_2$ as a substrate and the overcoming of hysteresis issues by chemically treating WS${}_2$ with a super-acid, which passivates these vacancies and strips the surface from contaminants. The hysteresis is significantly reduced below the noise level by at least a factor five (to $\Delta n<$5$\cdot$10${}^{10}$ cm${}^{-2}$) and, simultaneously, the room-temperature mobility of WS${}_2$-encapsulated graphene is as high as $\sim$6.2$\cdot$10${}^4$ cm${}^{-2}$V${}^{-1}$s${}^{-1}$ at a carrier density $n$ $\sim$1$\cdot$ 10${}^{12}$ cm${}^{-2}$. Our results promote WS${}_2$ to a valid alternative to hBN as encapsulant for high-performance graphene devices.

References in corpus (17)

• Electric Field Effect in Atomically Thin Carbon Films
• The Raman Fingerprint of Graphene
• Universal Dynamic Conductivity and Quantized Visible Opacity of Suspended Graphene
• Ultrahigh electron mobility in suspended graphene
• Boron nitride substrates for high-quality graphene electronics
• Electrochemically Top Gated Graphene: Monitoring Dopants by Raman Scattering
• Strong Photoluminescence Enhancement of MoS2 through Defect Engineering and Oxygen Bonding
• Realization of a High Mobility Dual-gated Graphene Field Effect Transistor with Al2O3 Dielectric
• Acoustic phonon scattering limited carrier mobility in 2D extrinsic graphene
• Single-crystal hexagonal boron nitride monolayer epitaxially grown on Cu (111) thin film across a wafer
• Mobility and Saturation Velocity in Graphene on SiO2
• Spontaneous doping of the basal plane of MoS2 single-layers through oxygen substitution under ambient conditions
• Graphene-Based Integrated Photonics For Next-Generation Datacom And Telecom
• Wafer-scale integration of graphene-based photonic devices
• Plasmon losses due to electron-phonon scattering: the case of graphene encapsulated in hexagonal Boron Nitride
• High-quality electrical transport using scalable CVD graphene
• Encapsulated graphene based Hall sensors on foil with increased sensitivity