Enhanced Field-Emission Performance from Carbon Nanotube Emitters on Nickel Foam Cathodes

Abstract

We present a three-dimensionally configured cathode with enhanced fieldemission performance formed by combining carbon nanotube (CNT) emitters with a nickel foam (NiF) substrate via a conventional screen-printing technique. The CNT/NiF cathode has low turn-on electric field of 0.53 V lm À1 (with current density of 10 lA cm À2 ) and threshold electric field of 0.87 V lm À1 (with current density of 0.1 mA cm À2 ), and a very high field enhancement factor of 1.4 9 10 4 . The porous structure of the NiF substrate can greatly improve the field-emission properties due to its large specific surface area that can accommodate more CNTs and increase the emitter density, as well as its high electrical and thermal conductivities that facilitate current transition and heat dissipation in the cathode. Most importantly, the local electric field was also enhanced by the multistage effect resulting from the rough metal surface, which furthermore leads to a high field enhancement factor. We believe that this improved field-emission performance makes such cathodes promising candidates for use in various field-emission applications.

Electronic Pulses from Pulsed Field Emission of CNT Cathodes

“…The average amplitude of electronic pulses is 0.027 mA/cm 2 and the fluctuation is less than 20% on applied voltage of 50 V. More important, the emission current density is nearly zero on laser pulse-off with applied voltage of 50 V, proving that electron emissions are excited only on the condition of laser pulse-on ( 1). The preliminary results show the realization of electron emission pulses from CNT cathodes and turn-on electric field less than 0.14 V/ m (turn-on electric field is defined as the electric field required to produce a current density of 0.01 mA/cm 2 ), which is incomparable with reference to previous studies, such as CNTs on nickel foam (0.53 V/ m) [28], graphene-CNT (0.73 V/ m) [29], CNTs on silicon pillars (2.16 V/ m) [30], and multilayer graphene-CNTs (0.93 V/ m) [31]. Actually, the turn-on voltage of the CNT cathodes was about 80 V (0.23 V/ m) by field emission.…”

Crack-Assisted Field Emission Enhancement of Carbon Nanotube Films for Vacuum Electronics

“…Among the numerous electron emitters, a thin film of CNTs is considered to be one of the most promising candidates. − Though many efforts have been made on the CNT cathode films, the FE performance is not yet satisfactory. Even now, most of the reported data for turn-on electric field ( E to ) and threshold electric field ( E th ) were higher than 1 V/μm despite a few examples. ,, In addition, the field emission stability needs further improvement due to the weak adhesion between CNTs and substrates and/or the susceptibility of pure CNTs to ion bombardment of residual air molecules in the strong electric field . Therefore, it is quite necessary to further improve the field emission performance of CNT films.…”

Field Emission from Lateral Multiwalled Carbon Nanotube Yarn Emitters

“…Various techniques have been studied to fabricate CNT emitters using as-grown, spraying, electrophoresis, and screen-printing methods, etc. She et al, 2003;Jeong et al, 2006;Jung et al, 2006;Chen et al, 2008Chen et al, , 2013Song et al, 2016). These techniques have mainly focused on field emission from a vertical configuration, i.e., field emission from the tip of CNTs (Jung et al, 2006;Chen et al, 2009Chen et al, , 2012.…”