Electron field emission from graphene nanosheets grown on Si nanoporous pillar array

Graphene nanosheet (GNS) thin film was grown flat lying on Si nanoporous pillar array (Si-NPA) substrate using Ni nanocrystallites as catalyst by a chemical vapor deposition method, and its field electron emission characteristics were studied. The thin film was proved to be composed of high-quality few-layer GNSs with a typical size of ~6 nm. With a turn-on field of ~2.85 V/μm, an emission current density of ~53.9 μA/cm2 was obtained at an electric field of 4.2 V/μm. Based on the experimental data, the enhancement factor of few-layer GNS/Si-NPA was calculated to be ~2700 according to the Fowler-Nordheim theory. The cold cathode also showed higher emission stability than vertically standing graphene at low operating voltages. For comparison, GNS/Si-NPA with multi-layer GNSs was prepared and its turn-on field was obtained as high as 8.5 V/μm. The origin of the high emission performance was attributed to numerous emission sites formed at the edges of GNSs, unique structure and morphology of GNS/Si-NPA, and low electric resistance of GNSs. Our results might have provided an alternative approach for fabricating Si-based low-voltage cold cathodes with high device performances.