Atomic force microscopy (AFM) was used to study the field emission (FE) properties of a dense array of long and vertically quasi-aligned multi-walled carbon nanotubes grown by catalytic chemical vapor deposition on a silicon substrate. The use of nanometric probes enables local field emission measurements to be made allowing the investigation of effects that are not detectable with a conventional parallel plate setup, where the emission current is averaged over a large sample area. The micrometric inter-electrode distance allows one to achieve high electric fields with a modest voltage. These features made us able to characterize field emission for macroscopic electric fields up to 250V/μm and attain current densities larger than 10^5A/cm^2. FE behaviour is analyzed in the framework of the Fowler-Nordheim theory. A field enhancement factor γ~40-50 and a turn-on field Eturn-on ~15V/μm at an inter-electrode distance of 1μm are estimated. Current saturation observed at high voltages in the I-V characteristics is explained in terms of a series resistance of the order of MΩ. Additional effects, such as electrical conditioning, CNT degradation, response to laser irradiation and time stability are investigated and discussed.

A local field emission study of partially aligned carbon-nanotubes by atomic force microscope probe

DI BARTOLOMEO, Antonio;SCARFATO, Alessandro;BOBBA, Fabrizio;CUCOLO, Anna Maria;
2007

Abstract

Atomic force microscopy (AFM) was used to study the field emission (FE) properties of a dense array of long and vertically quasi-aligned multi-walled carbon nanotubes grown by catalytic chemical vapor deposition on a silicon substrate. The use of nanometric probes enables local field emission measurements to be made allowing the investigation of effects that are not detectable with a conventional parallel plate setup, where the emission current is averaged over a large sample area. The micrometric inter-electrode distance allows one to achieve high electric fields with a modest voltage. These features made us able to characterize field emission for macroscopic electric fields up to 250V/μm and attain current densities larger than 10^5A/cm^2. FE behaviour is analyzed in the framework of the Fowler-Nordheim theory. A field enhancement factor γ~40-50 and a turn-on field Eturn-on ~15V/μm at an inter-electrode distance of 1μm are estimated. Current saturation observed at high voltages in the I-V characteristics is explained in terms of a series resistance of the order of MΩ. Additional effects, such as electrical conditioning, CNT degradation, response to laser irradiation and time stability are investigated and discussed.
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Utilizza questo identificativo per citare o creare un link a questo documento: http://hdl.handle.net/11386/2600376
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