Fabrication of gated cathode structures using an in situ grown vertically aligned carbon nanofiber as a field emission element

Abstract

Vertically aligned carbon nanofibers (VACNFs) are extremely promising cathode materials for microfabricated field emission devices, due to their low threshold field to initiate electron emission, inherent stability, and ruggedness, and relative ease of fabrication at moderate growth temperatures. We report on a process for fabricating gated cathode structures that uses a single in situ grown carbon nanofiber as a field emission element. The electrostatic gating structure was fabricated using a combination of traditional micro- and nanofabrication techniques. High-resolution electron beam lithography was used to define the first layer of features consisting of catalyst sites for VACNF growth and alignment marks for subsequent photolithography steps. Following metallization of these features, plasma enhanced chemical vapor deposition (PECVD) was used to deposit a 1-μm-thick interlayer dielectric. Photolithography was then used to expose the gate electrode pattern consisting of 1 μm apertures aligned to the buried catalyst sites. After metallizing the electrode pattern the structures were reactive ion etched until the buried catalyst sites were released. To complete the devices, a novel PECVD process using a dc acetylene/ammonia/helium plasma was used to grow single VACNFs inside the electrostatic gating structures. The issues associated with the fabrication of these devices are discussed along with their potential applications.