Impedance studies of layers with a vertical decay of conductivity or permittivity

摘要

Several types of dielectric layers on metals were investigated. It was observed that not only the CPE capacitance but also the CPE exponent #alpha# change if the thickness of the oxide layer, the thickness of the space charge layer or the pentration depth of water into an organic coating is changed. This behavior agrees with the predictions resulting from the theory of Young. The Young impedance can be considered as a more general model than the CPE for the description of the behavior of metals covered by dielectric layers. The measured frequency dependence of the phase angle #psi# can be explained with an exponential distribution of conductivity and/or permittivity across the dielectric layer perpendicular to the surface. If #psi# is nearly independent of frequency, the impedance response can be approximated by a simpel CPE.