Laser‐Assisted Phase Engineering of 2D MoS ₂ for Efficient Solution‐Processed Electronics

Phase engineering of two-dimensional transition metal dichalcogenides (2D TMDs), such as MoS₂, offers a powerful route for creating in-plane metal-semiconductor heterostructures and engineering low-resistance contacts in 2D electronics. Conventional strategies typically rely on chemically converting the semiconducting 2H phase into the metallic 1T/1T' polymorph, a multistep process prone to incomplete phase conversion. Local laser-induced transition of 1T/1T' into 2H MoS₂ offers a facile one-step alternative. However, employing this approach to engineer patterned electronic devices has remained elusive. Here, we demonstrate laser-assisted 1T'→2H phase patterning in phase-pure, solution-processed MoS₂, revealing the critical effect of irradiation atmosphere on phase transition. Although treatments in both ambient and inert environments produce apparent 2H Raman signatures, only inert-atmosphere irradiation yields micron-scale 2H domains within the 1T' lattice. Leveraging this controlled transition, we fabricate field-effect transistors with laser-patterned 1T'-2H-1T' lateral contacts that exhibit improved charge injection, as evidenced by order-of-magnitude higher mobility and ION/IOFF ratio, reduced hysteresis, and a ∼30% lower effective Schottky barrier height compared with conventional Au-2H contacts. These findings establish a robust and scalable route for functional laser-induced phase conversion in MoS₂ and provide a practical strategy for efficient and seamlessly integrated 2D electronic devices and circuits.