Georgia Tech researchers and ELSYS and SSC Pacific, respectively, have developed a thin-film triode design for CNT-based field emission to reduce the size and increase the efficiency of carbon nanotube (CNT)–based field emission devices, taking a major step toward achieving a portable source for electrons. This innovative triode design uses a dielectric layer to separate a conductive substrate from a counter-electrode (or gate electrode). Isotropic wet etching of an array of micron-scale pits in the dielectric layer enables bundles of CNTs to be synthesized in each pit through chemical vapor deposition. This approach creates a buffer zone around the CNTs, ensuring they are close to—but do not contact—the gate, which would cause a short. This design achieved a current density of 293 uA/cm2 at 200 V in a lightweight package, enabling the development of portable electron source devices.
- Requires very low operating voltage
- Yields a compact field emitter package
- Avoids electrical shorts caused by emitter-gate contact
- Offers better fabrication, eliminating construction and emitter growth defects
- Spacecraft electric propulsion
- Field emission (flat panel) displays
- X-ray sources
- Telecommunications equipment
- Vacuum electronics devices
Having a lightweight, efficient source of electrons is a major goal for spacecraft electric propulsion systems as well as a range of other applications. CNTs offer great promise for improved field emission performance given their very high electrical conductivity, high temperature stability, chemical inertness, and nanoscale geometry. However, CNT-based emitters face significant fabrication challenges. There is a need for a innovation that addresses those challenges.