Ethylene-glycol-assisted inkjet printing for controllable CVD growth of 2D MoS₂ single-crystal arrays

High-quality patterned growth of two-dimensional (2D) transition-metal dichalcogenides (TMDs) holds significant promise for next-generation electronics. In particular, inkjet printing combined with chemical vapor deposition (CVD) offers distinct advantages such as eliminating the need for seed crystals and masks. However, this method struggles to precisely control nucleation at predetermined sites at high temperatures, hindering concurrent improvements in single-crystal quality and array uniformity. To address this, we developed an ethylene glycol (EG)-assisted nucleation strategy coupled with a solid-liquid-solid (SLS) growth mechanism, enabling site-selective growth of predominantly monolayer MoS₂ single-crystal arrays with minor bilayer structures. During CVD, EG decomposes into reducing gases (e.g., H₂), which enhance the nucleation driving force while maintaining a clean interface. Simultaneously, the SLS mechanism confines nucleation spatially, suppressing site diffusion. The synergy of these effects ensures both array uniformity and high crystal quality. Using this strategy, we fabricated a highly ordered 15 × 15 MoS₂ single-crystal array with crystals up to ∼50 μm in size. The resulting transistors demonstrate carrier mobility of 1.306 cm² V^-1 s^-1 and an on/off ratio over 10⁴. This novel approach for patterned TMDs array growth is expected to advance their practical uses in integrated circuits, photodetectors, memory, and other 2D semiconductor electronics.