Electron Field Emission Enhancement of Vertically Aligned Ultrananocrystalline Diamond-Coated ZnO Core-Shell Heterostructured Nanorods

Enhanced electron field emission (EFE) behavior of a core-shell heterostructure, where ZnO nanorods (ZNRs) form the core and ultrananocrystalline diamond needles (UNCDNs) form the shell, is reported. EFE properties of ZNR-UNCDN core-shell heterostructures show a high emission current density of 5.5 mA cm(-2) at an applied field of 4.25 V m(-1), and a low turn-on field of 2.08 V m(-1) compared to the 1.67 mA cm(-2) emission current density (at an applied field of 28.7 V m(-1)) and 16.6 V m(-1) turn-on field for bare ZNRs. Such an enhancement in the field emission originates from the unique materials combination, resulting in good electron transport from ZNRs to UNCDNs and efficient field emission of electrons from the UNCDNs. The potential application of these materials is demonstrated by the plasma illumination measurements that lowering the threshold voltage by 160 V confirms the role of ZNR-UNCDN core-shell heterostructures in the enhancement of electron emission.