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=σ00·exp[−(T0/T)1/4] characteristic of 3D hopping, a linear correlation between the apparent Lnσ00(F) and T0(F) values, and a F/T3/2 scaling of σ(F,T). The F2 dependence of Lnσ(F,T) at intermediate fields, provides similar values of the decay length γ−1 of localized π state wavefunctions in a-CNx: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 sp2 phase.