Electrical and optical properties of semiconducting camphoric carbon films

In situ variation in resistance of camphoric carbon versus time of pyrolysis, temperature of pyrolysis and effect of sintering are studied to perceive the time required for the completion of pyrolysis and the activation energy from the electrical conductance plot. Variation in the electrical conductance versus temperature and activation energies derived from these measurements, are reproducible when film is thermally treated below 750 °C. Thermal treatment above 750 °C changes the anatomy of the film causing a change in the conductance profile as well as decreases its band gap to 0.1 eV. Camphor pyrolyzed at 650 °C gives semiconducting carbon with optical band gaps 1 eV (direct) and 0.8 eV (indirect). Increase in pyrolysis temperature also shifts G-band of Raman spectrum from 1605 to 1586 cm−1 i.e., towards value corresponding to graphitic carbon. SEM micrograph of camphoric film shows absence of any carbon nanobeads or fibers as normally observed with camphoric carbon pyrolysed in this temperature range.