Influence of Ti coatings on field emission characteristics of nano-sheet carbon films

Nano-sheet carbon films (NSCFs) coated with a 2-nm Ti layer were fabricated on n-type Si (110) by means of a quartz-tube-type microwave-plasma chemical-vapour-deposition (MWPCVD) method with hydrogen-methane gas mixture and an electron beam (EB) evaporation method. The field emission (FE) properties of the NSCF were changed by depositing a thin Ti film on its surface. The threshold field was decreased from 3.7 V/μm to 2.5 V/μm and the FE current density at a macroscopic electric field (E) of 10 V/μm was decreased from 41.7 mA/cm2 to 26.3 mA/cm2 for Ti-coated NSCFs. Moreover, the saturation tendency of the emission current density was not improved for Ti-coated NSCFs. A three-region E model considering statistical size effects of FE tip structures in the low E region and space-charge-limited-current (SCLC) effects in the high E region was proposed and the FE data in the low, middle and high E regions were reasonably interpreted.