Electron spin resonance study on high energy heavy ion irradiated conducting carbon films

Amorphous conducting carbon films are prepared by plasma assisted chemical vapour deposition. These films are irradiated by high energy (170 MeV) heavy ion (I-127(+13)) beam. As a result, the conductivity of the film is decreased by two to three orders of magnitude and a gap is created in its electronic structure. Two paramagnetic centres giving rise to the electron spin resonance (ESR) signals are observed in the irradiated films compared to a single one in the unirradiated film. Also the dependence of the ESR signal width and intensity on temperature and on microwave power is different in the irradiated films. Ion irradiation creates metastable states and carbon complexes in the films. ESR spectra throw some light on the mechanism of the structural change. (C) 1998 Elsevier Science Ltd.