High-field transport in amorphous carbon and carbon nitride films

The temperature and electric field dependence of the current density in hydrogenated amorphous carbon and carbon nitride sandwich devices show a T −1/4 dependence of the ohmic conductivity σ= σ 00·exp[−( T 0/ T) 1/4] characteristic of 3D hopping, a linear correlation between the apparent Ln σ 00( F) and T 0( F) values, and a F/ T 3/2 scaling of σ( F, T). The F 2 dependence of Ln σ( F, T) at intermediate fields, provides similar values of the decay length γ −1 of localized π state wavefunctions in a-CN x :H (2.4 nm) and a-C:H (2.8 nm) films. The larger conductivity in nitrogen-rich alloys is attributed to a combined effect of N-induced increase in the π-state density and ordering of the sp 2 phase.