High-mobility and air-stable single-layer WS2 field-effect transistors sandwiched between chemical vapor deposition-grown hexagonal BN films

Abstract

An emerging electronic material as one of transition metal dichalcogenides (TMDCs), tungsten disulfide (WS2) can be exfoliated as an atomically thin layer and can compensate for the drawback of graphene originating from a gapless band structure. A direct bandgap, which is obtainable in single-layer WS2, is an attractive characteristic for developing optoelectronic devices, as well as field-effect transistors. However, its relatively low mobility and electrical characteristics susceptible to environments remain obstacles for the use of device materials. Here, we demonstrate remarkable improvement in the electrical characteristics of single-layer WS2 field-effect transistor (SL-WS2 FET) using chemical vapor deposition (CVD)-grown hexagonal BN (h-BN). SL-WS2 FET sandwiched between CVD-grown h-BN films shows unprecedented high mobility of 214 cm2/Vs at room temperature. The mobility of a SL-WS2 FET has been found to be 486 cm2/Vs at 5 K. The ON/OFF ratio of output current is ~107 at room temperature. Apart from an ideal substrate for WS2 FET, CVD-grown h-BN film also provides a protection layer against unwanted influence by gas environments. The h-BN/SL-WS2/h-BN sandwich structure offers a way to develop high-quality durable single-layer TMDCs electronic devices.

Gate-Defined Quantum Confinement in InSe-Based van der Waals Heterostructures

“…Among the various TMDCs only a handful have shown sufficiently high , to observe 1D quantization. The possible contenders are fewlayer WSe2 and WS2 which exhibit  of around 500 cm 2 /Vs 24,25 and black phosphorus which has  up to ~5,000 cm 2 /Vs 26 at T=4 K. Recently, however, improvements in device fabrication have led to field-effect transistors made from MoS2 and InSe, which had  over 20,000 cm 2 /Vs 27,28 , high enough to observe the quantum Hall effect. Such mobilities make these materials promising candidates for the observation of 1D quantization.…”

High photoresponse of individual WS2 nanowire-nanoflake hybrid materials

“…Such a behavior is reasonable according to the equilibrium band diagram [inset in Fig. 1(b)] considering the work function ($5.6 eV) of Pt as well as the electron affinity ($4.0 eV), 14,15 work function ($5.1 eV), [16][17][18][19] and bandgap ($1.4 eV) of the WS 2 nanowire-nanoflake hybrid having p-type semiconducting behavior.…”

Quantum dot behavior in transition metal dichalcogenides nanostructures

“…Despite several attempts, the direct deposition of high quality highκ dielectrics on TMDCs remains an obstacle. Other TMDCs such as WSe2 and WS2 have also been demonstrated with excellent electronic properties and higher carrier mobilities [50][51][52], and therefore, they can exhibit similar or better potential for atomically thin electronics. To further improve the performance of TMDCs transistors, interface engineering, including TMDCs-dielectric and TMDCs-metal interfaces, is essential for minimizing contact resistance and interface scattering, which extremely restricts the mobility of carriers [53,54].…”