Effects of pretreatment and post-annealing on the field emission property of diamond-like carbon grown on a titanium/silicon substrate

Diamond-like carbon (DLC) films were deposited on titanium/silicon substrates with the help of the microwave plasma chemical vapor deposition (CVD) method with Ar, H2, and CH4 as a mixed gas source. Titanium/silicon substrates were polished by diamond powder and etched by hydrogen (H2) plasma, prior to deposition. After deposition, rapid thermal annealing (RTA) was used as a post-treatment. The effects of hydrogen plasma pretreatment and RTA post-treatment on the electron field emission characteristics of the DLC films was examined and correlated by Raman scattering, average surface roughness, and surface morphology. It is found that both treatments can improve the field emission characteristics of DLC films. However, RTA post-treatment demonstrates a more pronounced effect on the enhancement of field emission than does the hydrogen plasma pretreatment. This improvement is attributed in part to the increase in surface roughness resulting from sp2 clustering formed during the RTA. The tips of these sp2 clusters provide plenty of efficient emission sites on the surface of the DLC films. Another reason for this improvement is the graphene-like layers formed during the RTA, which provide efficient conduction paths for electrons to move through the DLC films. The field emission characteristics of CVD deposited on DLC films can be greatly enhanced by appropriate pretreatment and post-treatment, leading to promising applications for cold cathodes.