Employing a Bifunctional Molybdate Precursor to Grow the Highly Crystalline MoS ₂ for High-Performance Field-Effect Transistors

Growth of the large-sized and high-quality MoS ₂ single crystals for high-performance low-power electronic applications is an important step to pursue. Despite the significant improvement made in minimizing extrinsic MoS ₂ contact resistance based on interfacial engineering of the devices, the electron mobility of field-effect transistors (FETs) made of a synthetic monolayer MoS ₂ is yet far below the expected theoretical values, implying that the MoS ₂ crystal quality needs to be further improved. Here, we demonstrate the high-performance two-terminal MoS ₂ FETs with room-temperature electron mobility up to ∼90 cm ² V ^-1 s ^-1 based on the sulfurization growth of the bifunctional precursor, sodium molybdate dihydrate. This unique transition-metal precursor, serving as both the crystalline Mo source and seed promotor (sodium), could facilitate the lateral growth of the highly crystalline monolayer MoS ₂ crystals (edge length up to ∼260 μm). Substrate surface treatment with oxygen plasma prior to the deposition of the Mo precursor is fundamental to increase the wettability between the Mo source and the substrate, promoting the thinning and coalescence of the source clusters during the growth of large-sized MoS ₂ single crystals. The control of growth temperature is also an essential step to grow a strictly monolayer MoS ₂ crystal. A proof-of-concept for thermoelectric device integration utilizing monolayer MoS ₂ sheds light on its potential in low-voltage and self-powered electronics.