Light emission from vertically aligned carbon nanotube field emitters during Joule heating enhanced field emission

In this study, we present the observation and investigation of light emission from vertically aligned carbon nanotube (CNT) emitters induced by FE Joule heating using Poly(methyl methacrylate) (PMMA) thin film based field emission microscopy (FEM) method with microscopic video camera. This is the first time that investigation of the extended Schottky emission from vertically aligned CNT array based on the light emission directly observed. Due to the Joule heating, the electron emission of the incandescent CNT emitter transits from FE to extended Schottky emission and Schottky emission at a critical temperature of 1447 K. Experimental study shows that the effect of Joule heating at high FE current level ranges from 1.96 μA to 41.82 μA and averaging 11.82 μA. Finite element analysis results indicate that Joule heating of CNT emitters is almost an instantaneous process. An emission current of 11.82 μA is able to heat an emitter to over 2500 K. The maximum temperature on CNT increases with the decrease of CNT diameter and electric conductivity. The Schottky emission causes an increase of emission current before and after the CNT emitter failure. The appearance of light emission verifies that vertically aligned CNT FE enhanced by Joule heating is a self-heating Schottky emission.