Temperature and frequency dependent dielectric constant/loss studies in 50MeV Si+ ion irradiated kapton-H film

The kapton-H polyimide film samples (25 mum thickness) have been irradiated with 50 MeV Si+ ion beam with influences 2.3 x 10(12) and 1.38 x 10(13) io ns/cm(2). The dielectric constant/loss for irradiated samples have been mea sured in the temperature range 30-250 degreesC for different frequencies 12 0 Hz. 1 kHz, 10 kHz and 100 kHz. An increase in the low temperature (30-70 degreesC) low frequency epsilon' has been ascribed to the increase in water absorption capacity (gamma -relaxation) due to high energy ion irradiation . Dielectric loss maximum around 50()C is in conformity with this relaxatio n. The dielectric constant in temperature range 70-180 degreesC is mainly g overned by dipolar relaxation and space charge relaxation due to shallow en ergy traps. The epsilon' value for low flux sample is observed to be more t han that for high flux sample, It is suggested that though the space charge relaxation tends to increase epsilon'. a ma or loss in carbonyl groups due to high energy ion irradiation results in a decrease epsilon'. In high tem perature region (180-250 degreesC) the interfacial polarization due to crea tion of new phases hy irradiation increases the epsilon' value. The maximum in epsilon"-T curve at 250 degreesC confirms the presence of this relaxati on. However. in this temperature region increase in crystallinity of kapton -H results in a decrease of C. The dominance of any one determines the natu re of epsilon'-T curve.