Carbon Nanotube Field Emission Arrays

This effort exploits the unique physical and electrical characteristics of carbon nanotubes (CNTs) for field emission applications. Carbon nanotube field emission devices are designed, fabricated, and tested. Two reliable CNT synthesis methods, microwave plasma enhanced chemical vapor deposition (MPE-CVD) and thermal chemical vapor deposition (T-CVD), are developed. The physical properties of the resulting CNTs are analyzed using Raman spectroscopy and Scanning electron microscopy (SEM) and then tested for field emission performance. The T-CVD grown CNTs are shown to have fewer growth defects, but suffer from less process control making integration into devices difficult without further process development. Field emission testing shows the T-CVD CNTs to be much better emitters, exceeding 13 mA/cm2 at an electric field of only 1.4 V/micrometer, while the best MPE-CVD CNTs only managed 1 mA/cm2 at the much higher electric field of 4.56 V/micrometer. Two methods of device fabrication, conventional photolithography and nanosphere lithography, are developed and used to fabricate gated field emission arrays. Finite element analysis is used to optimize the gated array design to maximize the electric field strength. All fabrication steps are successfully demonstrated and prototype devices tested and compared to simple CNT carpet samples showing marked improvements by reducing electrostatic screening effects