Direct synthesis of micropillars of vertically aligned carbon nanotubes on stainless-steel and their excellent field emission properties

Vacuum micro/nano-electronics can greatly benefit from the improved emission current density and temporal stability of the electron beam due to the morphological control and direct contact of cold field-emitters on a conducting substrate. In this work, high-performance vertically aligned carbon nanotube (VACNT) pillar-based field-emitter arrays (VACNT-P-FEAs) were synthesized directly on stainless-steel (SS) via plasma-enhanced chemical vapor deposition. Nanosphere lithography was employed to limit the growth sites of VACNTs and form VACNT-P-FEAs of different sizes on the SS substrate. The field emission (FE) properties of the VACNT-P-FEAs were dependent on the size of the pillar emitters. Remarkable FE properties, such as low turn-on electric field (ETo = 1.57 V/μm), low threshold electric field (ETh = 2.94 V/μm), high field enhancement factor (β = 4977), and high emission current density (∼33 mA/cm2 at a field of 4 V/μm) were observed from the VACNT-P-FEAs grown using polystyrene microspheres (450 nm diameter) for lithography. The excellent FE performance can be ascribed to the inherent properties of the sample, such as the high conductivity of the SS substrate, low contact resistance between the SS substrate and VACNTs, the suitable number of active VACNT pillar field-emitters, and the reduced screening effect between the VACNT pillars.