Combinatorial evaluation for field emission properties of carbon nanotubes

Field emission properties of carbon nanotubes (CNTs) were comparatively evaluated by using combinatorial CNT libraries. The libraries were prepared by combinatorial masked deposition of a Co catalytic layer on Al₂O ₃/Si substrates and subsequent CNT growth by chemical vapor deposition from ethanol. Each library reproduced various types of single- and multiwalled carbon nanotubes with different morphologies and a variety of field emission properties. Combinatorial evaluations immediately identified the CNTs preferable as field emitters. The results obtained from individual field emission evaluations for samples with a constant nominal Co thickness agreed well with the results obtained from comparative evaluations for combinatorial CNT libraries. The results revealed that protrusive single-walled carbon nanotubes with a moderate interspacing showed the best field emission properties.