Two‐Step Electrophoretic Fabricated Sandwich‐Structured CNT Cold Cathode With Defect‐Coupled Multilevel NiO <i> _x </i> for Superior Field Emission

ABSTRACT Carbon nanotube (CNT) field emission cathodes have attracted considerable attention as electron sources owing to their low turn‐on fields and high current extraction capability. Nevertheless, practical application is hampered by intrinsic limitations, including current instability and rapid performance degradation, which stem from the structural state of the CNT film during emission and the strong dependence on the tunneling barrier. Herein, we report a post‐annealing deposited CNT (a‐d CNT) cold cathode emitter, fabricated via a two‐step electrophoretic method, featuring a multilevel NiO x structure with coupled CNT defects and a Ni–C–Cu sandwich‐like elemental distribution within the film. This emitter exhibits an ultralow current fluctuation rate of only 2.89% at 1.6 mA. The multilevel architecture effectively compresses the tunneling barrier ( φ = 4.74 eV) and superposes with the CNT field enhancement factor (overall β = 5444), enabling a low turn‐on field (1.25 V/µm). In addition, the high‐efficiency emission sites formed by defect bonding and the cross‐linked interface with the substrate establish highly efficient electrical and thermal transport channels. Consequently, the emitter demonstrates an 800% enhancement in current decay resistance relative to the pristine non‐annealed and non‐deposited CNT emitter (na‐nd CNT). This work provides a novel strategy for fabricating high‐performance CNT electron sources.