Electrical transport properties of Ni-doped diamond-like carbon films at and above room temperature.

The dielectric constant, impedance spectroscopy, ac conductivity, and dc conductivity of Ni-doped diamond-like carbon (DLC) films are reported within a wide temperature and frequency window. The dc conductivity increases with temperature, possessing different activation regions. At higher temperatures, a reversible semiconductor to metal transition is observed in the doped samples. Both the ac and dc conductivities are observed to increase with Ni doping concentration. However, the dc self-bias plays an important role in conductivity. The ac conductivity follows Jonscher's power law. The frequency exponent study shows that the ac conduction is governed by the correlated barrier hopping model. The grain boundary resistance is found to be higher than the grain resistance. According to the electric modulus study, the undoped DLC deviates from the ideal Debye behavior, with the deviation being higher in the high-frequency region. The current-voltage characteristics show a nonlinear hysteresis behavior. [ABSTRACT FROM AUTHOR]