Effect of back contact on field emission from carbon films deposited by very high frequency chemical vapor deposition

The effect of material and surface morphology of the back contact on field emission has been studied in carbon films deposited by very high frequency chemical vapor deposition at low temperature. The emission current was measured as a function of applied field for carbon films deposited simultaneously on various substrates coated with metals having different work functions (Ti, Cu, Ni, and Pt). Different metals demonstrated different types of microstructure and surface morphology. Therefore, the effect of back contact morphology was especially studied. The material of the back contact influenced the emission properties, but no direct correlation between emission and the work function of metal was observed. The field emission threshold was found to be affected by the roughness of the back contact: a Ti contact with 270 nm roughness showed emission threshold of Eth=3 V/μm, while a contact made of the same material, but with roughness of ∼2.5 nm had Eth=13 V/μm.