Boosted field emission properties and thickness effect of conductive polymers coated silicon carbide matrices for vacuum electronic devices

Boosted field emission (FE) cathodes of silicon carbide nanowires (SiC NWs) filled with polyaniline (PANI) and polypyrrole (PPY) coatings were prepared via cyclic voltammetry method, which is facile, feasible and capable to control the coating-thickness. As compared to pristine SiC, the average turn-on field (E_on) of SiC/PANI and SiC/PPY under several of repeat experiment decreased from 1.84 to 1.44 and 1.04 V/μm, respectively. The lowest E_on of SiC/PPY even dropped down to 0.95 V/μm with raised field enhancement-factor and conductivity, identifying that the FE properties have been improved by depositing PANI and PPY due to enhanced conductivity. However, the conductivity would be saturated with the continuously increasing depositing-thickness and overly thick coatings would block the efficient FE points and reduce the effective electric field between cathode and anode, causing a worse FE performance instead. Besides, the optimal FE performance was obtained in SiC/PPY, which not only had a much lower E_on, but also reinforced the stability. The synergy of conductivity effect and thickness effect found in this study indicates SiC/PPY to be a promising candidate for FE applications in vacuum electronic devices.