Estimation of optical band gap and carbon cluster sizes formed in heavy ion irradiated polycarbonate

Polycarbonate films (20 micron thick) were irradiated with 85 MeV oxygen and 100 MeV silicon ion beams at fluences that varied from 5×1011 to 1×1013 ions/cm2 were characterized with UV-visible spectroscopy. The optical band gap (Eg) values, calculated from the absorption edge in the 200-800 nm region using the Tauc relation, varied from 2.98 to 3.36 eV in oxygen irradiated samples and from 1.86 to 3.04 eV for silicon irradiated samples. The cluster size showed a range of 102-340 carbon atoms per cluster in both ion irradiations. The energy band gap in the cluster was found to decrease with transferred energy density of the ion beams.