Using plasma-enhanced chemical-vapor deposition with a gas mixture of CO and NH3, carbon nanotubes (CNTs) were vertically grown on a glass substrate with various catalyst metals and buffer layers. The effects of catalyst metals and buffer layers on the growth and emission characteristics of CNTs have been investigated. The difference in the field-emission characteristics between CNTs with various catalyst metals and buffer layers was mainly attributed to the crystallinity of CNTs, i.e., sp(2)-binding states of CNTs. These states could be the most effective electron-emission sites. (C) 2003 American Vacuum Society.