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

Abstract

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:N-2 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.