Plasma Knowledge-Based Polymorphic Engineering for Two-Dimensional Semiconductor Contacts

Two-dimensional (2D) transition metal dichalcogenides (TMDs) are widely regarded as front-runner channel materials for extending CMOS technology, yet their progress toward practical adoption has been fundamentally constrained by the absence of a scalable, foundry-compatible route to ultralow-resistance Ohmic contacts. Here, we demonstrate a CMOS-compatible plasma-ion-irradiation-driven phase transition that creates a polymorphic structure by spatially selective induction of the metallic 1T' phase within the semiconducting 2H phase in MoTe₂ and WS₂. By employing quantitative plasma-parameter metrology, we identify three ion-solid interaction regimes and determine the threshold ion-energy flux required to induce phase transition while avoiding etching or lattice degradation. Polymorphic edge contacts formed in this regime yield markedly reduced contact resistances down to 122 Ω·μm under the on-state gate bias. Precisely regulating the plasma kinetic energy flux allows modulation of the phase-transition depth, facilitating the fabrication of edge-contacted MoTe₂ devices with enhanced on-current up to 68.15 μA/μm, on/off ratios exceeding 10⁷, a record-high mobility of 1.61 × 10⁴ cm²/V·s, and excellent current saturation and stability. This work establishes a generalizable framework for plasma-enabled phase engineering in 2D materials and offers a realistic, manufacturable pathway toward integrating polymorphic TMD contacts into next-generation intelligent CMOS.