Influence of the distribution of local field enhancement factors on the shape of the current-voltage characteristics of carbon-nanotube-based large-area emitters

Abstract Experimental current-voltage characteristics (IVCs) of carbon nanotube (CNT)-based large-area field emitters (LAFEs) were measured and analyzed using a “two-class model”, in which some emitters had a set of local field enhancement factors (FEFs) significantly larger than those of the other emitters. An online measurement of the experimental IVCs was carried out and, interestingly, showed the presence of strong nonlinearity in the form of “upward bends” in the corresponding orthodox Fowler-Nordheim (FN) plots. Our studies were conducted over a wide range of currents, and excellent agreement between our experimental results and the proposed theory confirmed the general validity of the two-class FEF model of orthodox field emission. The results presented here were also supported by a bimodal distribution of the brightness level observed by an analysis of the glow patterns, since the brightness was expected to depend on the site's emitted current. We believe this is an important step for LAFE characterization when strong nonlinearites are present in the FN plots, since an FEF similar to the classically defined FEF was recently proven to be applicable to CNTs in the context of full quantum ab initio calculations.