Failure Mechanisms and Stability Enhancement for Carbon Nanotube Field Emission Cathodes

Carbon nanotube field emission cathodes (CNT‐FECs) have emerged as a promising next‐generation electron source, distinguished by low turn‐on fields and the potential to output high current. However, CNT‐FECs suffer from current instability and rapid emission degradation due to multiple failure mechanisms. In this review, the failure mechanisms in CNT‐FECs are analyzed, focusing on three aspects: (1) failures at the substrate/CNT interface, driven by weak van der Waals contact and thermal expansion mismatch, leading to detachment under high electrical and thermal stresses; (2) emitter degradation, resulting from carbon oxidation, evaporation, and arcing under non‐uniform electric fields and Joule heating; (3) gate deterioration, manifested through carbonaceous byproduct accumulation, gate oxidation, and ion bombardment‐induced structural damage. Strategies addressing these issues are discussed, including: (1) interfacial covalent engineering via buffer layers or adhesion layers for enhancing the mechanical and thermal stabilities; (2) structural and material modification on emitters for improving the electric field uniformity and reducing the work function; (3) modified gate designs, such as multilayer and electret‐coated configurations, to focus electron beam for boosting the electron transmittance. Advances in materials engineering and designs are establishing a detailed roadmap toward CNT‐FECs with enhanced operational stability, elevated current density, and expanded practical applications.