Effect of pyrolyzing time and temperature on the bandgap of camphor-pyrolyzed semiconducting carbon films

Intrinsic p- and n-type semiconducting carbon thin films have been synthesized by the pyrolysis of camphor vapor in an argon atmosphere at various temperatures for different periods of time. These films are characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscope (SEM) analyses, Hall measurement and electrical conductivity studies. The nature of conductivity of camphor-pyrolyzed semiconductors is found to be extremely sensitive to the pyrolyzing temperature and time. It is observed that an sp(2) content in the as-grown film of less than 33% yields a p-type semiconductor, whereas more than 33% sp(2) makes it n-type. The percentage contents of sp(2) and sp(3) carbon can be controlled by the temperature and time of pyrolysis. (C) 1998 Elsevier Science S.A. All rights reserved.