Semiconducting carbon films from a natural source: camphor

Abstract

Thin films of carbon have been grown on alumina substrates by the pyrolysis of camphor at 900 degrees C for 2h in an argon atmosphere, followed by sintering for various time periods. The effect of sintering time on the surface morphology, conductivity, carrier concentration, mobility and bandgap of camphor-pyrolyzed films is discussed. Structural characterizations are performed on the basis of XRD and SEM analyses. Electrical conductivity measurements of these films, as a function of temperature, suggest them to be semiconductors. Hall-effect study of the as-grown films shows their carrier concentrations to be of the order of 10(17) cm(-3). The Hall mobilities of these films are found to vary from 1702 to 10263 cm(2) V-1 s(-1). The thermal bandgaps of these films are found to decrease with increasing sintering time. Thus, by controlled sintering of camphor-pyrolyzed carbon films, it is possible to obtain a semiconductor with the desired bandgap. Therefore, camphor-pyrolyzed semiconducting carbon films seem to be a promising material to develop a photovoltaic solar cell. (C) 1999 Elsevier Science S.A. All rights reserved