US Patent 7064474 - Tapered Nanotube Array

http://www.freepatentsonline.com/7064474.pdf

As noted in the previous posting, vertical nanotube arrays have been around for several years now with the major current application being flat panel displays and with future applications such as parallel electron beam lithography (for high volume nanoscale fabrication) looking promising. However, one hurdle for this technology is the field screening effect which basically limits the current density produced from closely spaced electron emitting nanotubes. This patent proposes an interesting configuration to reduce the field screening effect by tapering the lengths of groups of nanotubes at spaced intervals greater than 1 micron. Claim 1 reads:

1. A carbon nanotube array comprising: a plurality of carbon nanotubes, the carbon nanotubes being parallel to each other and cooperatively forming a plurality of lower portions and a plurality of corresponding tapered tips above the lower portions; wherein distances between adjacent tips are approximately uniform, and the distance is more than one micrometer.