NaCl-Assisted One-Step CVD for In-Plane 1T/1H Heterophase Homojunctions in Monolayer WS₂

Two-dimensional WS₂ offers promising advantages for various applications due to its semiconducting 1H phase and metallic 1T phase. However, the instability of the 1T phase and the difficulty of achieving a stable phase coexistence present significant challenges. Here, we adopt the NaCl-assisted one-step chemical vapor deposition method that enables the spatial coexistence and precise control of 1H and 1T phases within monolayer WS₂. The phase diagram establishes a clear correlation between precursor ratios and the structural phases of WS₂. Density functional theory calculations reveal the stability difference between the 1H and the 1T phases at the electronic level. Calculated work functions are consistent with experimental Kelvin probe force microscopy, confirming the electronic properties of the heterophase interface. This work provides a scalable and efficient approach for phase engineering in WS₂, with great potential for advancing optoelectronic devices and catalytic systems.