Thickness Dependent Dielectric Loss of Plasma Poly (Ethylene Oxide) Films

Abstract

Dielectric properties of plasma poly (ethylene oxide) (pPEO) thin film samples were investigated at room temperature. The thin film samples with different thicknesses were deposited by plasma assisted physical vapor deposition (PAPVD) technique at 5 W plasma discharge power. The thicknesses were 20, 100, 250, 500 nm. It was observed that dielectric constant increases with increasing thickness. The relaxation times determined by dielectric loss-frequency relation, shift toward higher frequencies with increasing thickness. In addition film thickness, heating processes were defined as another parameter. By this purpose, thin film samples were heated and cooled, respectively. It was observed that maxima and minima of dielectric loss at cooling process take place at lower frequencies in comparison with frequencies at which maxima and minima were detected at heating process. These results may show the effect of dead layer at thinner films. After heating process, it was observed from behavior of dielectric constant and dielectric loss that the crosslinking density increases by heating effect. This effect may cause additional reactions between free radicals which are production of PAPVD. Moreover, dynamic glass transition temperatures were calculated. These temperatures prove the effect of dead layer approximation.