Field-emission from carbon nanotube cones fabricated by micro-electro-discharge machining

Field-emitters based on patterned carbon nanotube (CNT) arrays have promising properties. For example, they operate at low voltages and produce significant current. To pattern carbon nanotube arrays into various shapes, the typical approach consists of using lithography to pattern the catalyst prior to nanotube growth. However, this technique enables only two-dimensional patterning, where the height of the nanotubes remains unchanged. It is highly desirable to tailor the shape of CNT arrays in three dimensions (3D) in order to optimize the field emission performance of the arrays, including height control and creating angled surfaces. Here, we report on the polishing of the top surface of a CNT forest pillar and creation of cone-type structures in CNT arrays, similar in shape to the emitters in a conventional field-emitter array based on bulk metals. For this, we use dry micro-electro-discharge machining (μEDM) in oxygen ambient. We also report the results of field-emission experiments from them and show that the beam resulting from the CNT cone produces a sharp, uniform emission spot on the phosphor screen in field-emission microscopy.