Giant Thickness‐Tunable Bandgap and Robust Air Stability of 2D Palladium Diselenide

Uncovering the thickness‐dependent electronic property and environmental stability for 2D materials are crucial issues for promoting their applications in high‐performance electronic and optoelectronic devices. Herein, the extrahigh air stability and giant tunable electronic bandgap of chemical vapor deposition (CVD)–derived few‐layer PdSe2 on Au foils, by using scanning tunneling microscope/spectroscopy (STM/STS), are reported. The robust stability of 2D PdSe2 is uncovered by the observation of nearly defect/adsorption‐free atomic lattices on long‐time air‐exposed samples. A one‐to‐one correspondence between the electronic bandgap (from ≈1.15 to ≈0 eV) and thickness of PdSe2/Au (from bilayer to bulk) is established. It is also revealed that few‐layer semiconducting PdSe2 flakes present zero‐gap edges, induced by hybridization of Pd 4d and Se 4p orbitals. This work hereby provides straightforward evidence for the thickness‐tunable electronic property and air stability of 2D semiconductors, thus shedding light on their applications in next‐generation electronic devices.