Study of the Optical Properties and the Carbonaceous Clusters in Thermally-annealed CR-39 and Makrofol-E Polymer-based Solid-state Nuclear Track Detectors

The induced modifications in the optical properties of CR-39 and Makrofol-E polymer-based solid-state nuclear track detectors were investigated after thermal annealing at a temperature of 200 degrees C for different durations. The optical properties were studied using an UV-visible spectrophotometer. From the UV-visible spectra, the direct and the indirect optical band gaps, Urbach's energies, and the number of carbon atoms in a cluster were determined. The absorbance of CR-39 plastic detector was found to decrease with increasing annealing time while the absorbance of Makrofol-E decreased with increasing annealing time. The width of the tail of localized states in the band gap Delta E was evaluated with the Urbach method. The optical energy band gaps were obtained from the direct and the indirect allowed transitions in K-space. Both of the direct and the indirect band gaps of the annealed CR-39 detector decrease with increasing annealing time while in Makrofol-E, they decreased after an annealing time of 15 minute and then showed no remarkable changes for a prolonged annealing times. Urbach's energy decreased significantly for both CR-39 and Makrofol-E with increasing annealing time. The number of carbon atoms in a cluster increased in the CR-39 detector with increasing annealing time while it decreased with increasing annealing time for Makrofol-E. We may conclude that the CR-39 detector undergoes greater modifications than the Makrofol-E detector upon thermal annealing at 200 degrees C. In conclusion, the induced modifications in the optical properties of CR-39 and Makrofol-E are correlated with the temperature and the duration of annealing.