Numerically optimized bundle size and distribution of carbon nanofibers for a field emitter

To obtain good field emission (FE) properties, the array and distribution of carbon nanofiber (CNF) bundles were evaluated with a computation system tool. A simulation program was constructed on the basis of the surface charge method originally, and a three-dimensional model was used to calculate the FE properties. In this study, the field enhancement factor β for FE property depended on the diameter of a CNF bundle and the distance between adjacent CNF bundles, and a good correlation was obtained between the experimental and computed results for FE employing an original calculation program. For these results, we attempted to optimize the array of CNF bundles to achieve good FE characteristics. The above-mentioned β and the emission site area α important for FE are considered in this paper. Although it was very difficult for the FE evaluation to deal with α, we designed the array using an experimentally determined α. As a result, CNF bundles morphology with good FE characteristics was achieved when the CNF bundle size was close to 0.4 μm, which results in maximum current. It was possible to predict FE property with a computation model.