Abstract
Here we report on a straightforward and rapid means of enhancing the field electron emission performance of nascent vertically aligned multi-walled carbon nanotubes by introducing a polar zwitterionic conjugated polyelectrolyte adlayer at the vacuum-emitter interface. We attribute the observed 66% decrease in turn-on electric field to the augmented emitter micro-morphology and shifted surface band structure. The composite emitters can be optically modulated by exploiting the absorption cross-section of the solution cast adlayer, which increases the local carrier concentration which broadens the effective electrostatic shape of the emitter during optical excitation. Assessment via scanning anode field emission microscopy reveals a 25% improvement in DC time stability, a significant reduction in long-term hysteresis shift, and a threefold increase in bandwidth during pulsed mode operation.
Highlights
Electron emission technologies are ubiquitous; from X-ray sources[1] and electron microscopes,[2] to travelling wave tubes,[3] microwave amplifiers,[4] high dynamic range displays,[5,6] and free electron lasers.[7]
We find that our zwitterionic conjugated polyelectrolytes (ZCPEs) adlayer mediates a fourfold decrease in free carrier concentration at the upper most emission surface which reduced the deleterious effects of nearest neighbour shielding common to highly-packed carbon nanotube based emitters
ZCPE, F(NSO3)[2] synthesis is described in detail elsewhere.[22]
Summary
Electron emission technologies are ubiquitous; from X-ray sources[1] and electron microscopes,[2] to travelling wave tubes,[3] microwave amplifiers,[4] high dynamic range displays,[5,6] and free electron lasers.[7]. The MWCNT* densified samples have a comparable field enhancement factor to the ZCPE coated devices, suggesting that crack formation in the adlayer has an analogous effect to the morphology changes in the MWCNT*.
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