Engineering the field emission properties of graphene film by gas adsorbates.

We study the effect of different gas adsorbates (N2, O2, and CO2) on the field emission (FE) properties of graphene film. Our experimental measurements show that, except for N2, adsorption of O2 and CO2 reduces the FE current of the graphene film. Moreover, the measured FE hysteresis loop is almost quenched after adsorbing O2 or CO2. The ab initio calculations quantify the experimental results by predicting a larger work function and smaller FE current for the graphene system after O2 or CO2 adsorption. In contrast, the change of FE properties in N2 adsorbed graphene is negligible. A "depolarization electric field model" is then proposed to explain the observed FE hysteresis behavior.