Schottky barrier formation on r.f.-plasma enhanced chemical vapour deposited hydrogenated amorphous carbon

This paper reports the fabrication and electrical characterization of sub-micron metal contacts to thin films of hydrogenated amorphous carbon deposited by the r.f.-plasma enhanced chemical vapour deposition technique. The I–V characteristics of “large” area (diameter 0.5 mm) top metal contacts to amorphous carbon are consistent with bulk limited conduction by the Poole–Frenkel mechanism. The I–V characteristics of sub-micron metal contacts, formed at different locations on the same amorphous carbon film, range from symmetrical to highly asymmetrical with forward-to-reverse rectification ratios up to three orders of magnitude. Asymmetrical I–V characteristics and a linear C−2–V response confirm, for the first time, Schottky barrier formation at the metal/amorphous carbon interface. Spatial non-uniformity in the composition of the hydrogenated amorphous carbon surface is indicated, which mirrors bulk inhomogeneity.