Patterned growth and field emission properties of vertically aligned carbon nanotubes

Vertically aligned carbon nanotubes were grown selectively on patterned Ni thin films by microwave plasma-enhanced chemical vapor deposition and their field emission properties were investigated using a diode-structure. Ni th in films patterned with a form of dot-arrays were prepared using a shadow m ask having an array of holes. The nanotubes were found to be well-graphitiz ed with multiwalled structures. The measurements of field emission properti es revealed that the carbon nanotube tips emitted high current density at l ow macroscopic electric field. The Fowler-Nordheim (F-N) plot clearly showe d two characteristic regions where the current saturates at the high electr ic field region. It was found that the saturation behavior was caused by th e adsorbates-enhanced field emission mechanism. Eliminating the adsorbates resulted in no saturation behavior, increasing turn-on field, decreasing cu rrent, and increasing field enhancement factor. Using ZnS/Cu,Al phosphor, v ery bright and uniform emission patterns were obtained. (C) 2001 Elsevier S cience B.V. Adl rights reserved.