Synthesis and field emission properties of periodic arrays of vertically aligned carbon nanotubes on copper

Periodic arrays of carbon nanotubes (CNTs) with different densities were synthesized on copper substrate by employing nanosphere lithography (NSL) and plasma enhanced chemical vapor deposition. Vertically aligned CNTs were formed using Ni as catalyst at a growth pressure of 8 torr of C$_{2}$H$_{2}$/NH$_{3}$ mixture and a temperature of 520\r{ }C. Electron emissions of the CNTs with different densities were investigated to reveal the dependence of the electron emission properties of the CNTs on their densities. Experimental results showed that low-density CNTs exhibited better field emission properties as compared to the high-density CNTs. Low-density CNTs exhibited lower turn-on and threshold electric fields, and a higher field enhancement factor. The high density of CNTs resulted in the deterioration of the FE properties due to the screening of the electric field by the adjoining CNTs.