Thermally stimulated depolarization current behaviour of 50 MeV Li+ ion-irradiated kapton-H polyimide film

Different dielectric relaxation processes such as dipolar and space charge have been investigated in high-energy ion-irradiated kapton-H polyimide usi ng thermally stimulated discharge current (TSDC) technique. Kapton-H sample s (12.5 mum thickness) are irradiated with Li+ ion (50 MeV) at different fl ux ( 5 x 10(5), 10(5), 10(4) ions/cm(2)) at Nuclear Science Center, New Del hi (PELLETRON Facility). The thermoelectret of irradiated samples are prepa red following the usual method for various poling fields and temperatures. The TSD currents are obtained at heating rate of 2 degreesC/min. The peak a ppearing at low temperature and associated with dipolar polarization is lar gely affected in irradiated samples. This is mainly due to the dimerization of the carbonyl groups. The high temperature peak which is associated with space charge relaxation becomes more pronounced in irradiated samples. Hig h-energy ion-irradiation provides deep energy trap centers in the form of c onjugated bonds due to de-localized electrons. Low temperature tail of TSDC shows many kinks. These kinks are due to creation of new cross-linking dep endent sub polar groups and shallow energy traps as a result of high-energy ion-irradiation.