Experimental confirmation of the nearly power-law relation between macroscopic current and characteristic current density in carbon nanotube-based large-area field emitters

Abstract

Carbon nanotube (CNT) films are potential candidates for viable applications in large-area field electron emission based X-ray sources. An important issue in large-area field electron emitters (LAFEs) is the connection between the macroscopic emission current iM and the characteristic current density JC, linking experimental observations to field emission theories. The quantity JC is often associated with the site in the LAFE with the maximum field enhancement factor (FEF). This convention is used in practice because it mimics the one used for single-tip field emitters. Within the mainstream Fowler-Nordheim (FN) theory, a linear relation between iM and JC is expected. However, recent theoretical works within the framework of the standard FN theory have predicted a nearly power-law dependence between these two quantities. This work experimentally confirms those theoretical predictions for CNT-based LAFEs. Experimental studies, supported by glow pattern analysis, were conducted over a wide range of emitted currents and, importantly, confirm the general validity of the two-component FEF for CNT-based LAFEs, which can be viewed as a simple approach to this nearly power-law dependence.