Principal Investigator Luis Velasquez-Garcia (Heller)
In field emission, electrons are ejected from a solid surface via quantum tunneling due to the presence of a high local electrostatic field. Compared to state-of-the- artthermionicelectronsources,fieldemissioncathodes consume significantly less power, are faster to switch, and could operate at higher pressure. Field emission cathodes have a wide range of applications such as X-ray sources, flat-panel displays, and electron microscopy.
Several materials, e.g., Si, ZnO, and graphene, have been explored as field emission sources; however, carbon nanotubes (CNTs) are very promising to implement field emission cathodes due to their high aspect ratio, high electrical conductivity, excellent mechanical, and chemical stability, and high current emission density. Reported approaches for fabricating CNT field emitters include screen printing and direct growth of nanostructures (e.g., plasma-enhanced chemical vapor deposition) where a static stencil, i.e., mask, is involved to produce patterned structures in specific locations. These masks increase the time and cost needed to iterate the pattern, affecting the prototype optimization of the cathode. Ink direct writing (IDW), i.e., the creation of imprints by extrusion of liquid suspensions through a small nozzle, has emerged as an attractive maskless patterning technique that can accommodate a great variety of materials to create freeform imprints at low-cost. An imprint with CNTs protruding from the surface of the imprint, strongly adhered to the substrate can achieve stably high-current emission when an electric field is applied. We are currently working on the design and optimization of the formulation of a CNT-based ink, to eventually demonstrate low-cost field emission sources.