Characterizing field emission from individual carbon nanotubes at small distances

Abstract

This article demonstrates the characterization of field emission from individual carbon nanotubes (CNTs) attached to a tungsten tip, when the separation distance s between the anode and tip of the CNT (cathode) is less than 15μm. The separation distance is adjusted with a nanopositioning stage after establishing a datum by detecting the anode surface with the CNT tip. Our separation distance s differs by the height h of the CNT from the distance d that is often measured between the planar anode and the planar substrate of an emitting cathode. Consequently, the electric field at the tip of the CNT is modeled by F=λV∕s, where λ is our field amplification factor, rather than by F=γV∕d, where γ is the more conventional field enhancement factor. Twenty-four sets of current-voltage I(V) data were measured from an individual multiwall CNT at separation distances s between 1.4 and 13.5μm. A nonlinear curve-fitting algorithm extracted Fowler-Nordheim (FN) parameters from each set of I(V) data, rather than conventional extraction from the FN plots. The turn-on voltage Vto (to emit 1nA) as a function of the separation distance followed an empirical power relation Vto=asb, and the field amplification factor λ empirically followed the relation λ=λ∞s∕(s+h)+1. This experimental characterization is an improvement over other techniques since the gap is controlled more precisely over a larger range, the electric field at the CNT tip is not disturbed by other CNTs, and the anode is flat to within a few nanometers.

Carbon Nanotube Field Emission Devices with Integrated Gate for High Current Applications

“…Figure 3a shows the field emission I-V characteristics of a CPA with a turn-on voltage of 0.9 V/μm. This low turn-on field of CPAs is comparable to values typically reported for individual CNT emitters [7,8].…”

Effect of substrate heating and microwave attenuation on the catalyst free growth and field emission of carbon nanotubes

“…7 shows field emission measurement results on the samples A, B and C respectively. It is known form the previous works [15,18,39,40] that field emission from CNTs is governed by Fowler-Nordheim (F-N) equation as given below [39][40][41].…”

Field emission from a single carbon nanofiber at sub 100nm gap

“…9 There have been extensive theoretical studies of the effects on the geometrical shape and interelectrode distance of a single CNT. [10][11][12] However, the experimental study of the field emission properties from a single CNT or CNF at nanometer regime gap is scarce. It is attributed to the challenge in resolving the separation in sub 100 nm.…”