Hybrid structure of graphene sheets/ZnO nanorods for enhancing electron field emission properties

A hybrid structure of graphene sheets (GSs)/ZnO nanorods (ZNRs) is developed on glass substrates for applications in field emission (FE) cathodes. ZNRs are grown on glass substrates by a combination of sputtering and hydrothermal processes. Graphene films are synthesized on the Cu foils by the thermal chemical vapor deposition technique, and are transferred onto the ZNRs with various cycles (one, two, and three times) to form GS/ZNR hybrids with different morphology. FESEM, XRD, and Raman spectroscopy are used to analyze the surface morphology, crystallinity, and chemical composition, respectively. It is found that the FE properties of all GS/ZNR cathodes possess a lower turn-on electric field and higher current density than pristine ZNR cathode owing to the presence of the GS. The GSs/ZNRs with two transferred cycle exhibit the lowest turn-on electric field (3.7 V/μm, 1 μA/cm2) and highest enhancement factor β (8723). These superior properties indicate that the GS/ZNR hybrids are promising field cathodes in FE applications.