Water vapor-induced structure modification of vertically-aligned carbon nanotube arrays and successive thin film coating for enhanced field emission properties

Vertically-aligned carbon nanotubes (VCNTs) are used as electron source in various field emission applications owing to its high aspect ratio, chemical inertness, mechanical strength and electrical conductivity. Here, we demonstrate that surface structure modification along with thin film coating enhances the field emission performance, such as turn-on voltage, emission site density, and stability. In the present study, VCNTs with different heights were grown on silicon wafers by thermal chemical vapor deposition followed by the structure modification of VCNTs using capillarity-driven water vapor condensation. We obtained various surface morphologies by varying the water vapor exposure time and heating temperature. In addition, the structure-modified VCNTs surfaces were coated with W and SiO₂ thin films using electron-beam evaporation. It was observed that W-coated VCNTs with modified surface morphology results in the best field emission performance.