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Two-dimensional transition metal dichalcogenides (TMDs) offer numerous advantages over silicon-based application in terms of atomically thin geometry, excellent opto-electrical properties, layer-number dependence, band gap variability, and lack of dangling bonds. The production of high-quality and large-scale TMD films is required with consideration of practical technology. However, the performance of scalable devices is affected by problems such as contamination and patterning arising from device processing; this is followed by an etching step, which normally damages the TMD film. Herein, we report the direct growth of MoSe2films on selective pattern areas via a surface-mediated liquid-phase promoter using a solution-based approach. Our growth process utilizes the promoter on the selective pattern area by enhancing wettability, resulting in a highly uniform MoSe2film. Moreover, our approach can produce other TMD films such as WSe2films as well as control various pattern shapes, sizes, and large-scale areas, thus improving their applicability in various devices in the future. Our patterned MoSe2field-effect transistor device exhibits a p-type dominant conduction behavior with a high on/off current ratio of ∼106. Thus, our study provides general guidance for direct selective pattern growth via a solution-based approach and the future design of integrated devices for a large-scale application.

A single-layer MoS2achieves excellent gate controllability within the nanoscale channel length of a field-effect transistor (FET) owing to an ultra-short screening length. However, multilayer MoS2(ML-MoS2) is more vulnerable to short channel effects (SCEs) owing to its thickness and long screening length. We eliminated the SCEs in an ML-MoS2FET (thickness of 4–13 nm) at a channel length of sub-30 nm using a Schottky barrier (SB) variable graphene/ML-MoS2heterojunction. Although the band modulation in the ML-MoS2channel worsens with a decrease in the channel length, which is similar to the SCEs occurring in conventional FETs, the variable Fermi level (EF) of a graphene electrode along the gate voltage allows control of the SB at the graphene/MoS2junction and backs up the current modulation through a variable SB. Electrical measurements and a theoretical band simulation demonstrate the efficient SB modulation of our graphene nanogap (GrNG) ML-MoS2FET with three distinct carrier transports along Vgs: a thermionic emission at a low SB, Fowler–Nordheim tunneling at a moderate SB, and direct tunneling at a high SB. Our GrNG FET shows an extremely high on–off current ratio of ∼108, which is approximately three-orders of magnitude better than a previously reported metal nanogap (MeNG) FET and a self-aligned metal/graphene nanogap FET with a similar MoS2thickness. Our GrNG FET also exhibits a 100,000-times higher on–off ratio, 100-times lower subthreshold swing, and 10-times lower drain induced barrier.