Nickel oxide-1D/2D carbon nanostructure hybrid as efficient field emitters

Sharp one-dimensional (1D) and two-dimensional (2D) structures are required for stable and efficient field emission. 1D metal oxide and 1D carbonaceous nanostructure material have been used widely for exciting field emission applications. On the other hand, planar, continuous 2D nanostructures have been less explored, as most often, they offer inefficient field emitters, having high turn-on field and low emission current density. A combination of 1D and 2D nanostructures is expected to improve field emission properties. In the present study, nickel oxide nanostructures were considered as 1D nanostructures, which were synthesized on cleaned, polished, nickel foil substrate by wet chemical treatment through the nano-seed mechanism. Pyramidal shape nanostructures of NiO were found onto nickel substrate. 1D nanostructure, NiO nanostructure, does not show any field emission response. Further, graphene oxide (GO) was used as the 2D nanostructure.) While nickel oxide nanostructure and graphene oxide individually demonstrated very low emission properties, hybrid of these materials show modified surface topography and enhanced field emission properties. The field emission response of graphene oxide on Ni foil shows 6.7 V/μm turn-on field and maximum current density of 28 µA/cm², whereas graphene oxide on NiO nanostructure has enhanced field emission response. In the case of NiO–GO, the turn-on field and maximum current are 5 V/μm and 173 µA/cm², respectively. Field emission properties are enhanced further with the reduction of the NiO–GO hybrid and depositing CNT of NiO. The maximum current density of 3.7 mA/cm²was observed for the NiO–CNT hybrid.