Field emission microscopy of graphene on iridium point emitter

The field electron emission from the surface of an iridium point emitter covered by a monolayer graphene film has been studied. An analysis of the field emission images showed that electron emission takes place at the boundaries between graphene islands with dimensions up to several dozen nanometers. Intercalation of alkali metal (cesium) atoms under the graphene film decreases the work function of the emitter but does not change the image. Field ion desorption images obtained in the fields where the surface diffusion of Cs atoms is impossible reveal the presence of a submonolayer concentration of cesium at the defects representing graphene island contacts.