In situ observation and evaluation of individual emitter tips in titanium nitride-coated, volcano-structured field emitter arrays

In this study, a method for measuring the emission current of a single emitter tip in a multitip field emitter array (FEA) was proposed using a field electron emission microscopy (FEEM) system. The measured emission current was attenuated owing to the presence of apertures along the optical axis in the measurement instrument; therefore, the recorded values were only a fraction of the actual emission current. To overcome this issue, a method was proposed for measuring the emission current of a single emitter tip based on its ratio to the total current emitted by the entire FEA. Using this method, the emission current from a single emitter tip could be quantitatively measured, allowing for direct comparison of the emission current before and after surface treatments. Furthermore, changes in the number of active emitter tips were evaluated in the FEEM mode. The number of active emitter tips considerably increased after the initial thermal treatment. In particular, the number of active emitter tips increased from 49 to 99 out of 100 at a gate voltage (Vg) of 50 V. Owing to aging, the emission current of the emitter tip with the highest current reduced from 36% to 11% of the total emission current. This resulted in the averaging effect of multiple emitters and improved the stability of the FEA (standard deviation/mean current reduced to <2%). These findings collectively confirmed the effectiveness of the treatment methods employed herein.