Carbon nanofibers were grown on flexible polyimide substrates using an ion-beam sputtering technique. Field emission measurement showed a fairly low threshold voltage of 1.5V∕μm with a current density of 1μA∕cm2. The field enhancement factor was determined to be 4400. The emitter showed resilience when exploited as a high voltage electron source for x-ray generation. The x-ray generated by the flexible emitter is capable of delivering fine images of biological samples with superior sharpness, resolution, and contrast.

The process of deriving emission-area estimates from Fowler-Nordheim ͑FN͒ plots is investigated, using emission-area extraction functions and an iterative procedure suggested earlier ͓R. G. Forbes, J. Vac. Sci. Technol. B 17, 526 ͑1999͔͒. Simulated FN-plot data have been prepared using free-electron theory and three different tunneling-barrier models ͑elementary triangular barrier, image-rounded ''Schottky-Nordheim'' barrier, and a quadratically enhanced barrier͒. These have been analyzed using two area-extraction spreadsheets with different models ͑elementary triangular barrier and Schottky-Nordheim barrier͒ embedded in them. It is confirmed that significant errors in the area estimate may occur if the emission model used to analyze the FN-plot data does not correspond well with the model/physics responsible for generating the data. It is also concluded that parameters used in the area-extraction process should correspond to emission variables in the midrange of the FN-plot data.

The authors present the fabrication and electrical characterization of carbon nanofiber-based flexible field emitters prepared by an ion beam technique. The flexible emitters are extremely robust under various stress conditions and show no sign of degradation after 16h long lifetime test. An all-plastic flexible field emission device with excellent emission properties has also been demonstrated using phosphor-coated polyester as an anode.

The authors report the electron field emission from a single carbon nanofiber (CNF) over a range of anode to CNF tip separations of 20–5500nm. Our results show that the field enhancement factor γ is associated with the electrode separation (S). The modified Miller equation is a reasonable empirical model to describe the behavior of γ, which varies with S over a large range of values. The γ approaches to an asymptotic value of 415 or 1 when S is very large or very small as compared to the length of the CNF, respectively. The maximum field emission current sustained by the single CNF without causing damage was estimated to be as high as 15μA.

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