Direct patterned growth of intrinsic/doped vertical graphene nanosheets on stainless steel via heating solid precursor films for field emission application

Vertical graphene nanosheets (VGNs), normally consisting of one to several graphene layers vertically aligned on substrates, are promising in a variety of applications including field electron emitters, gas sensors and energy storage devices. Herein, we report a simple, green, easily scalable and cost-effective strategy of growing both intrinsic and nitrogen (N)-doped VGNs on stainless steel (SS) just by heating the solid thin layers of glucose and/or urea in a resistance-heating furnace. It is interesting that VGNs mainly grow on the roughened regions, which can be attributed to the more nucleation and catalyzing sites on such regions than smooth SS. Meanwhile, the N doping concentration can be adjusted by varying the urea addition. Field electron emission measurement indicates that the obtained N-doped VGNs exhibit excellent field emission with a relatively low turn-on electric field strength (~2.6 V μm−1 at the current density of 10 μA cm−2), large field enhancement factor (~9428) and high stability.