Coulomb explosion of vertically aligned carbon nanofibre induced by field electron emission

Abstract

Carbon nanofibre (CNF) field emitter failure is often encountered but there is a lack of understanding of its degradation behaviour and mechanism. This study, starting with a direct observation of a light emission followed by an Coulomb explosion, presents a systematic characterization of CNF emitter failure using a PMMA (poly(methyl methacrylate)) thin film based field emission microscopy (FEM) method. This unique CNF emitter failure behaviour is due to a combined effect of Joule heating and excessive charging at high FE current, ranging from 1.95 μA to 41.82 μA. Joule heating converts FE to extended Schottky emission and heats CNFs almost instantaneously. With the aid of Joule heating, Coulomb explosions disintegrate CNFs and generate annular craters of 60–70 μm on the PMMA thin film, melted areas of 10–20 μm on the substrate, and a sputter of PMMA around the emission sites in a range of 100–120 μm. This study successfully explains the behaviour and mechanism of CNF absence after FE, which is often simply attributed to uprooting or burnout of the CNFs. The detailed study of Coulomb explosion of CNF induced by FE allows the systematic design and optimization of CNF FE devices for long-lasting operation.