Layer-by-Layer Thinning of PdSe₂ Flakes via Plasma Induced Oxidation and Sublimation

Controlled O₂/Ar plasma exposure and subsequent low temperature inert atmosphere annealing of chemical vapor deposition (CVD) grown PdSe₂ flakes etch PdSe₂ layer-by-layer in an atomic layer etching-like (ALE) process. X-ray photoelectron spectroscopy (XPS) shows that exposure to a remote inductively coupled plasma (ICP) oxygen plasma oxidizes the top layer of the PdSe₂ to form PdO₂ and SeO₂. After an in situ annealing, XPS shows no trace of PdO₂ or SeO₂, suggesting the byproducts are volatile at low temperature. Atomic force microscopy of PdSe₂ exposed to various O₂ + Ar plasmas (O₂ = 25-100%) demonstrates a clear trend between the oxygen concentration and the number of layers etched per cycle. PdSe₂ field effect transistors (FETs) were characterized at various stages of two ALE-like cycles, and the electrical properties are correlated to the oxidation and byproduct desorption and layer reduction.