Field emission properties of selectively grown carbon nanotubes for electron emitters in microwave power amplifier

We have directly grown CNTs on the metal substrates by direct-current plasma-enhanced chemical-vapor deposition (DC-PECVD) using a gas mixture of C₂H₂ and NH₃ at relatively low temperature (550 °C). In this study, we report field emission properties of CNTs depending on pattern sizes and spacings. Field-emission characteristic of CNTs was evaluated in a vacuum of 10^-6 Torr in a parallel diode configuration. It is found that there is a correlation between pattern morphologies (such as window area, spacing, and dimension of window edge, etc.) and the field-emission properties. Furthermore, we found that the contact resistance between CNTs and substrate is a crucial factor for the saturation of field emission from CNTs.