D.C. conductivity measurements on amorphous conducting carbon

Amorphous conducting carbon films are obtained by pyrolysis of PTCDA (perylene tetracarboxylic dianhydride) at different temperatures (in the range 700–1000 °C) and their d.c. conductivity is studied as a function of temperature in the range 4.2–300 K. It is observed that the conductivity has an activated temperature dependence with small activation energies (0.02-0.004 eV). The effects of pyrolysis temperature and also of heat treatment after preparation are studied. It is observed that the conductivity increases and the activation energy decreases with the increasing pyrolysis temperature. Heat treatment of samples at temperatures higher than that of pyrolysis has a similar effect on properties, even though the structure does not appear to depend appreciably on the pyrolysis temperature.