Quantitative characterization of field emission parameters: Application to statistical analysis of individual carbon nanotubes/nanofibers

Abstract

In this study, the authors present a detailed procedure for the quantitative measurement of the field emission properties of a large number of vertically aligned carbon nanotubes/nanofibers (CNs) using a scanning anode field emission microscope (SAFEM). This method provides the statistical distribution of all the relevant emitter parameters such as field enhancement factor, emitter height, and maximal current before failure. In order to extract the correct absolute enhancement factor of each CN, an analytical electrostatics model has been developed taking into account for the “tip-to-tip” geometry of anode and cathode in the SAFEM set-up. This analytical model has been validated by finite elements electrostatic simulations. Experimental measurements of enhancement factor distributions determined at several anode–cathode distances show the importance of this procedure to obtain quantitative correct values. A good correlation between the enhancement factor and the CN length has been observed. Additionally, the correlation between the maximum current before failure and the enhancement factor has also been investigated. Unlike in previously reported experiments, no clear dependence between these two parameters has been obtained. This result can be explained in our case by a large dispersion of CN crystalline quality or CN–substrate electrical contact resistance in the array used in this study.