Direct growth of MoS2 on electrolytic substrate and realization of high-mobility transistors

Although electrostatic gating with liquid electrolytes has been thoroughly investigated to enhance electrical transport in two-dimensional (2D) materials, solid electrolyte alternatives are now actively being researched to overcome the limitations of liquid dielectrics. Here, we report direct growth of few-layer (3-4L) molybdenum disulfide (MoS2), a prototypical 2D transition metal dichalcogenide (TMD), on lithium-ion solid electrolyte substrate by chemical vapor deposition (CVD), and demonstrate a transfer-free device fabrication method. The growth resulted in 5-10 mu m sized triangular MoS2 single crystals as confirmed by Raman spectroscopy, x-ray photoelectron spectroscopy, and scanning electron microscopy. Field-effect transistors (FETs) fabricated on the as-grown few-layer crystals show near-ideal gating performance with room temperature subthreshold swings around 65 mV/decade while maintaining an ON/OFF ratio around 10(5). Field-effect mobility in the range of 42-49 cm(2) V-1 s(-1) and current densities as high as 120 mu A/mu m with 0.5 mu m channel length has been achieved, back-gated by the solid electrolyte. This is the highest reported mobility among comparable FETs on as-grown single/few-layer CVD MoS2. This growth and transfer-free device fabrication method on solid electrolyte substrates can be applied to other 2D TMDs for studying advanced thin-film transistors and interesting physics, and is amenable to diverse surface science experiments, otherwise difficult to realize with liquid electrolytes.