Effect of oxygen adsorption on electron transport in few-layer InSe FETs*

The oxidation effect in 2D chalcogenides is a well-known problem in 2D materials. We investigate the adsorption of oxygen molecules on the surface of few layer InSe FETs through trans-conductance and time dependent conductance measurements. We observe a positive shift of threshold voltage when few-layer InSe FET devices are exposed to oxygen (corresponding to a reduction in electron density in the order of 10¹² /cm² for an oxygen pressure of 60 Torr) which is partially reversible through applying gate stress. Time dependent measurements show a drop in conductivity up to a factor of 5 when exposed to 5 Torr of oxygen gas, over the time scale of the order of 1000 seconds. From these results, we characterize the oxygen sensing response of few-layer InSe devices, and discuss the implications on the underlying binding interaction between oxygen molecules and InSe. Nitrogen exposure, on the other hand, did not yield appreciable change in InSe FET's characteristics.