Posttreatment-dependent current degradation and role of tube length on morphology of printed carbon nanotube field emitters

Field-emission current was degraded very fast down to less than 20% from its initial maximum in a few min when the printed carbon nanotubes were activated with adhesive tape. Conversely, initial increasing behavior and ne ligible degradation over 10 h were observed from samples treated with a soft-rubber roller. The severe destruction of nanotube skeletons and residual contaminants on tube walls induced by taping were interpreted to lead to the fast degradation of current. In addition, we show that the vertical alignment of nanotubes is strongly affected by tube length. Although 2-5-pm-long tubes were well aligned through field emission, nanotubes with a length of 100 mu m or larger showed a seriously entangled morphology leading to nonuniform emission images.