Doping-Free All PtSe₂ Transistor via Thickness-Modulated Phase Transition

Achieving a high-quality metal contact on two-dimensional (2D) semiconductors still remains a major challenge due to the strong Fermi level pinning and the absence of an effective doping method. Here, we demonstrate high performance "all-PtSe₂" field-effect transistors (FETs) completely free from those issues, enabled by the vertical integration of a metallic thick PtSe₂ source/drain onto the semiconducting ultrathin PtSe₂ channel. Owing to its inherent thickness-dependent semiconductor-to-metal phase transition, the transferred metallic PtSe₂ transforms the underlying semiconducting PtSe₂ into metal at the junction. Therefore, a fully metallized source/drain and semiconducting channel could be realized within the same PtSe₂ platform. The ultrathin PtSe₂ FETs with PtSe₂ vdW contact exhibits excellent gate tunability, superior mobility, and high ON current accompanied by one order lower contact resistance compared to conventional Ti/Au contact FETs. Our work provides a new device paradigm with a low resistance PtSe₂ vdW contact which can overcome a fundamental bottleneck in 2D nanoelectronics.