Flexible and free-standing well-aligned carbon nanotube arrays have been synthesized on super-aligned carbon nanotube films. The combined structure of the carbon nanotube array and carbon nanotube film was formed during chemical vapor deposition on a quartz substrate which had previously been covered with a super-aligned carbon nanotube film. It was found that the growing carbon nanotube array could support up the super-aligned carbon nanotube film entirely, and the top of the array became densely entangled with the super-aligned carbon nanotube film. The carbon nanotube array with the super-aligned carbon nanotube film could be easily peeled off from the quartz substrate as a whole, giving a flexible and free-standing structure with good mechanical properties. The bottom of the array was also exposed after being peeled off and was used as a field emitter. The combined structure of the carbon nanotube array with the carbon nanotube film allowed adsorbent-free field emission by passing a heating current through it. Furthermore, due to the fast thermal response of the structure and the long time needed for re-adsorption of adsorbates in vacuum, it was found that pulsed heating with a 10% duty ratio was sufficient for adsorbent-free field emission. The heating power necessary to sustain the adsorbent-free state can be lowered in this way.

Open image in new window