Characterization of field emission properties of glass frit-based CNT pastes prepared using high-energy milling

CNT field emitters have been frequently fabricated by screen-printing CNT paste because this process is easy, scalable, and inexpensive. In order to secure high performance and reliability for CNT field emitters, however, some aspects need to be considered, such as paste adhesion, CNT dispersion in the paste, height uniformity of CNTs, etc. In this study, paste adhesion was improved by engaging nanometer-sized glass frit (GF) filler. In addition, the nanometer-sized GF also helped level the paste surface, which further made CNTs protrude with similar heights. With the nanometer-sized GF, field emission properties including a turn-on electric field, emission uniformity, and lifetime were enhanced significantly. Dispersion of CNTs in the paste was increased by applying high-energy milling. However, excessive milling was found to damage CNTs and degraded their field emission properties. The amount of CNTs and GF in the paste also played a key role in determining field emission performance of CNT emitters. The ratio of CNTs to GF was optimized to maximize the number of working CNT emitters while maintaining their cohesion in the paste. It was observed that the paste adhesion could be evaluated by sheet resistances of the sample measured before and after surface activation. A large increase of the sheet resistance implied weak adhesion of the CNT paste. The sheet resistances of the CNT pastes after activation were further discussed by relating to their field emission properties.