Tunable Current Transport in PdSe₂ via Layer-by-Layer Thickness Modulation by Mild Plasma

The thickness-modulated phase transition from semi-metallic (bulk) to semiconductor (a few layers) is the most unique property of pentagonal palladium diselenide (PdSe₂). Thus, precise thickness tailoring is essential to fully utilize its unique thickness-dependent property for exotic device applications. Here, tunable current transport in PdSe₂ based field-effect transistors (FETs) enabled by layer-by-layer thinning of PdSe₂ using mild SF₆:N₂ plasma is presented. With this top-down plasma-etching method, the PdSe₂ layer thickness can be precisely modulated without structural degradation, which paves the way to realize the complete potential of PdSe₂-based devices. By modifying the plasma power and exposure time, an atomic layer precision etching rate of 0.4 nm min⁻¹ can be achieved. Atomic-force microscopy, Raman spectroscopy, and secondary ion mass spectrometry confirm the uniform and complete removal of top layers of PdSe₂ flake over a large area without affecting remaining bottom layers. Electrical characterization of current transport in plasma-thinned PdSe₂ FETs reveals excellent layer-dependent conductivity similar to pristine PdSe₂ FETs. This simple but highly scalable and controllable plasma-etching technique provides a promising way to fabricate PdSe₂ devices based on lateral heterostructures composed of different thicknesses PdSe₂ flakes to exploit strongly thickness-dependent electronic structures.