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|Title:||Temperature and frequency dependent dielectric constant/loss studies in 50 MeV Si+ ion irradiated kapton-H film|
Quamara, J K
|Abstract:||The kapton-H polyimide film samples (25 μm thickness) have been irradiated with 50 MeV Si+ ion beam with fluences 2.3×1012 and 1.38×1013 ions/cm2. The dielectric constant/loss for irradiated samples have been measured in the temperature range 30-250 oC for different frequencies 120 Hz, 1kHz,10 kHz and 100 kHz. An increase in the low temperature (30-70oC) low frequency ε' has been ascribed to the increase in water absorption capacity (γ-relaxation) due to high energy ion irradiation. Dielectric loss maximum around 50oC is in conformity with this relaxation . The dielectric constant in temperature range 70-180oC is mainly governed by dipolar relaxation and space charge relaxation due to shallow energy traps. The ε' value for low flux sample is observed to be more than that for high flux sample. It is suggested that though the space charge relaxation tends to increase ε', a major loss in carbonyl groups due to high energy ion irradiation results in a decrease of ε'. In high temperature region (180- 250oC) the interfacial polarization due to creation of new phases by irrad iation increases the ε' value. The maximum in ε"-T curve at 250oC confirms the presence of this relaxation. However, in this temperature region increase in crystallinity of kapton-H results in a decrease of ε'. The dominance of any one determines the nature of ε' -T curve.|
|ISSN:||0975-1041 (Online); 0019-5596 (Print)|
|Appears in Collections:||IJPAP Vol.39(07) [July 2001]|
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