The efficiency of the high-power, high-voltage (HV) insulation system is currently approaching a saturation level due to the limited availability of the high-quality resistive stress-grading material that can withstand ever-increasing applied voltage at very low insulation-wall thickness. A unique non-rectifying, non-linear current-voltage characteristic is observed in ZnO nanoparticle-anchored carbon nanofiber (ZnO-CNF) hybrid thin film devices, which has novel applications in non-linear stress-grading materials for high-voltage devices and overvoltage protectors in multifunctional electronic circuits. A simple chemical precipitation method is used to fabricate the hybrid films, followed by vacuum-annealing at elevated temperatures. Interestingly, the organic surfactant (Triton X-114), used as binder during the film deposition, manifests unintentional carbon-doping into ZnO lattice, which leads to a conductivity inversion of ZnO from n-type in lower-temperature (300 ºC) annealed hybrid into p-type in the higher-temperature (600 ºC) annealed film. The novelty of this work is that, the CNF-ZnO interface acts as a metal-semiconductor (M-S) junction, where high conducting CNF acts as the metal and ZnO NPs as the semiconducting (n- or p-type) counterpart (denoted as MCNF-Sn/p-ZnO junction). The band-energy calculations have revealed that the barrier height at the MCNF-Sn/p-ZnO junction is quite low to manifest non-rectifying characteristics (i.e. the I-V curves are near-symmetric in both forward and reverse directions). Additionally, a large number of C-atoms (from the surfactant) are not only doped into the ZnO lattice, but also reside at the ZnO-CNF interface as trap states. Electrical characterizations reveal that the CNF-ZnO interfaces act as a metal-semiconductor junction with low barrier height, leading to non-rectifying junction properties. Also the surfactant-induced C-atoms create trap-states at the interface which ‘emit’ the trapped charges via interfacial field-assisted tunneling, thus imposing non-linearity (in both forward and reverse directions) on the I-V curves.