Producing air-stable InSe nanosheet through mild oxygen plasma treatment

Ultrathin indium selenide (InSe), as a newly emerging two-dimensional material with high carrier mobility and broadband optical absorption, is considered as a promising candidate for electronic and optoelectronic devices. It has been a challenge to produce air-stable mono-or few-layer InSe nanosheets because they degrade rapidly in an ambient environment. Here, we demonstrate a facile mild oxygen plasma treatment route to fabricate air-stable few-layer InSe samples. Photoluminescence (PL) and x-ray photoelectron spectroscopy (XPS) analysis indicate that the plasma treatment can introduce an oxidation process that forms a dense InSe1-xOx capping layer on the surface, and thus prevent the sample from degradation. Furthermore, the oxide layer would introduce a PL quenching of the pristine InSe, while a new and strong PL peak belonging to the emission from InSe1-xOx appears. This work offers a practical and efficient route to improve the performance of InSe based electrical and optoelectronic devices.