Field emission characteristics of nano-sheet carbon films deposited by quartz-tube microwave plasma chemical vapour deposition

Nano-sheet carbon films are prepared on Si wafers by means ofquartz-tube microwave plasma chemical vapour deposition (MPCVD) in agas mixture of hydrogen and methane. The structure of the fabricatedfilms is investigated by using field emission scanning electronmicroscope (FESEM) and Raman spectroscopy. These nano-carbon filmsare possessed of good field emission (FE) characteristics with a lowthreshold field of 2.6,V/$mu $m and a high current density of12.6,mA/cm$^{2}$ at an electric field of 9,V/$mu $m. As the FEcurrents tend to be saturated in a high $E$ region, no simpleFowler--Nordheim (F--N) model is applicable. A modified F--N modelconsidering statistic effects of FE tip structures and aspace-charge-limited-current (SCLC) effect is applied successfullyto explaining the FE data observed at low and high electric fields,respectively.