Direct Laser Patterning and Phase Transformation of 2D PdSe Films for On-Demand Device Fabrication.

Heterophase homojunction formation in atomically thin 2D layers is of great importance for next-generation nanoelectronics and optoelectronics applications. Technologically challenging, controllable transformation between the semiconducting and metallic phases of transition metal chalcogenides is of particular importance. Here, we demonstrate that controlled laser irradiation can be used to directly ablate PdSe thin films using high power or trigger the local transformation of PdSe into a metallic phase PdSe using lower laser power. Such transformations are possible due to the low decomposition temperature of PdSe and a variety of stable phases compared to other 2D transition metal dichalcogenides. Scanning transmission electron microscopy is used to reveal the laser-induced Se-deficient phases of PdSe material. The process sensitivity to the laser power allows patterning flexibility for resist-free device fabrication. The laser-patterned devices demonstrate that a laser-induced metallic phase PdSe is stable with increased conductivity by a factor of about 20 compared to PdSe. These findings contribute to the development of nanoscale devices with homojunctions and scalable methods to achieve structural transformations in 2D materials.