Surface disordering and its correlations with properties in argon implanted CR-39 polymer

Abstract

The influence of Ar+ implantation induced disordering in the surface layers of the CR-39 polymer on its optical properties and surface hardness has been studied. The specimens were implanted at 130 keV to the doses of 5 × 1014, 1 × 1015, 1 × 1016 Ar+ cm−2. The structural behavior of the pre- and postimplanted specimens was investigated using UV-Visible, Raman, and x-ray diffraction techniques. Formation of disordered graphitelike structures in the implanted layers of polycarbonate has been observed using Raman and UV-Visible spectroscopy. A significant increase in the value of disorder content (Urbach energy) from 0.77 eV to 1.48 eV and a continuous decline in optical bandgap (from 3.43 eV to 2.32 eV) with increasing implantation dose have been observed. This decrease in optical bandgap has been found to have linear dependence on the increase in the Urbach energy, which points toward the formation of disordered structures in the implanted layers of CR-39 polymer. Further, Knoop microhardness is found to be enhanced by a factor of 7 (at a load of 9.8 mN) after implantation. The possible correlation of the increase in Knoop surface hardness with the changes observed as a result of implantation has been established and discussed.