Enhanced field emission properties of aligned sharp graphene emitter arrays prepared by freeze-drying and hydrothermal reduction

Reduced graphene oxide bundles with sharp tips were fabricated by a simple approach with freeze drying and hydrothermal reduction, and this approach could modify the surface topography of the field emission cathode and make more graphene bundles sharpen and aligned. This field emission cathode material displayed excellent field emission properties decreased from 2.9 V mu m(-1) to a low turn-on field of 0.8 V mu m(-1) at the emission current density of 10 mu A cm(-2). Sharp graphene emitter arrays have sharp protruded tips in abundance, leading to an enlarged field enhancement factor from 1683 to 10182, which was much better than those films prepared by other methods we adopted. It also revealed a good field emission stability with no degradation in the current for 3 h. We believe that this approach can enhance the field emission performance of graphene emitters, which could be widely candidate for various field emission applications.