Influence of Annealing Temperature on Berthelot-Type Hopping Conduction Mechanism in Carbon-Nickel Composite Films

Electrical conductivity of carbon-nickel composite films annealed at temperatures 300,500 and 800℃ is studied over a temperature range of 50-300 K.While the conductivity data above room temperature show extended state conduction,lowering the temperature from 150 to 50 K leads to the Berthelot-type conduction mechanism.It can be seen that the films annealed at 500℃ have the maximum conductivity.The extent of the carrier wave function at 500℃ has the minima 2.87 × 10-7cm and 2.45 × 10-7cm in octahedral-metal stretching vibrations and intrinsic stretching vibrations of the metal at the tetrahedral site,respectively.The average distances between two vibration octahedral and tetrahedral sites at 500℃ also have the minima 1.13 × 10-7cm and 0.97 × 10-7cm,respectively.The Berthelot temperature for films annealed at 800℃ has the minimum of 94.3K.