Electrostatic Shielding in Patterned Carbon Nanotube Field Emission Arrays

As the morphologies of patterned carbon nanotube (CNT) field emission arrays become more complex, it is critical to examine the interactions of individual emitters in close proximity to one another. The number of active emission sites in dense arrays can be severely inhibited by electrostatic shielding. To explore this effect, we have fabricated an array of microscale CNT bundles with varying diameters. Field enhancement was found to increase with decreasing bundle diameter. High-resolution scanning electron microscopy revealed a corresponding increase in the number of stray CNT tips as the bundle diameter decreased. These CNT tips were not as heavily shielded, resulting in improved emission current density. Our results confirm that electrostatic shielding significantly affects the field enhancement of dense arrays, particularly in terms of the number of emitters actively participating in the field emission process.