Computational simulation and phenomenological analysis of freestanding carbon nanotube coulomb explosion induced by field emission

After the occurrence of a Coulomb explosion and its negative effects on carbon nanotube (CNT) field emission (FE) were first discovered by our group recently, the specific causes of the Coulomb explosion and reducing the possibility of Coulomb explosion are considered to be the main challenges relating to improving the lifetimes and increasing the emission currents of CNT field emitters. In this study, we designed a cathode of freestanding CNTs to observe the degradation and Coulomb explosion of CNTs during FE. A high-speed camera was used to capture the Coulomb explosion phenomenon, which occurs in an instant accompanied by a flash of light, causing strong arcing and leaving a large crater on the cathode. The Coulomb explosion is mainly induced by the high Coulomb energy accumulated on the tips of the CNTs due to the ionization of carbon atoms during FE, and there is no time for free electrons to recover these ions. A simulation was conducted based on the experimental results to verify the mechanism of the FE-induced Coulomb explosion. The Coulomb energy, bond energy, and kinetic energy in a CNT model at each time point are calculated. Through the study, the causes of FE-induced Coulomb explosion have been thoroughly understood, which is critical for optimizing the design of a longer-lifetime CNT cathode.