Magnetic catalyst residues and their influence on the field electron emission characteristics of low temperature grown carbon nanotubes

We report the electron paramagnetic resonance characteristics of catalytic residues for in situ grown carbon nanotube field electron emitter and present direct evidence that field electron emission in carbon nanotube sheets grown on various catalytic nanodots/SiO₂-coated Si substrate with low-pressure chemical vapor deposition is influenced by the magnetism of catalytic metals and thus the electrical properties of the nanotubes. The nanotubes with weak trace of ferromagnetism, which originated from the catalysts, show lower turn-on emission field and higher electron emission current than those with distinct ferromagnetic properties. A strong relationship between the ferromagnetism of nanocrystalline catalysts and field electron emission characteristics of nanotubes can be utilized for the development of an efficient carbon nanotube based-field electron emitter.