Novel inkjet printing system and formation mechanism of PdO nanofilms for field-emission imaging devices

We have developed a new inkjet printing system with high landing accuracy of ink droplets, and high uniformity of the width and profile of films for PdO nanofilm emitters in large-area field-emission imaging devices. The inkjet system has a temperature- and humidity-controlling unit and a vacuum chamber. The ink droplets can be printed with high accuracy in a high-humidity-environment. The droplets of the ink used in this study were pinned during a vacuum drying process and transformed into elliptical ringlike Pd precursor films. Next, the films were dissolved and transformed into droplets by humidification. The droplets were then dried again with various evaporation rates. As a result, the Pd precursor films were transformed into films with a nearly flat surface having the same in-plane size as the droplets. After annealing, PdO nanofilms with 80 ± 5 μm width and 4.4 ± 0.7 nm thickness having the same uniform profiles were obtained.