Effects of coffee ring via inkjet printing seed layers on field emission properties of patterned ZnO nanorods

Inkjet printing, a fast, simple, efficient graphical deposition technology, is first applied to achieve high-quality emission arrays. Patterned arrays of ZnO nanorods have been successfully synthesized via hydrothermal method after inkjet printing the ZnO seed layer. During printing, different substrate temperatures were found to affect the morphology, microstructure and field emission (FE) properties of ZnO arrays. The results showed that the FE performance was improved when the coffee ring effect was eliminated by raising the substrate temperature due to higher aspect ratio of the nanorods. Both the compensating flow characteristics inside the droplets and the mechanism of regulating the rheological behavior of the solution during inkjet printing were analyzed to inhibit the effect of coffee ring, which played an important role in the later patterning electrode construction of emission arrays. The selective growth of the emitter material can be easily realized by introducing the direct patterning technology of inkjet printing in the preparation of field emission electron source.