Layer-by-Layer Thinning of PdSe 2 Flakes via Plasma Induced Oxidation and Sublimation

Controlled O 2 /Ar plasma exposure and subsequent low temperature inert atmosphere annealing of chemical vapor deposition (CVD) grown PdSe 2 flakes etch PdSe 2 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 PdSe 2 to form PdO 2 and SeO 2 . After an in situ annealing, XPS shows no trace of PdO 2 or SeO 2, suggesting the byproducts are volatile at low temperature. Atomic force microscopy of PdSe 2 exposed to various O 2 + Ar plasmas (O 2 = 25–100%) demonstrates a clear trend between the oxygen concentration and the number of layers etched per cycle. PdSe 2 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.