RELAXATION PROCESSES IN INSULATOR THIN-FILMS

Relaxation peaks with the same activation energy as the DC conductivity have been observed in the low-frequency dielectric properties of insulator thin films. In particular, we present results for electron-beam-evaporated aluminium oxide films and sputtered hydrated nickel oxide films. The presence of the relaxation peaks seems to be correlated to the amount of hydrogen atoms present in the films. We propose a phenomenological model for the relaxation process. It is assumed that the DC conductivity is due to charge-carrier transport in electronic states positioned at a certain energy above the Fermi level. The energy difference between the Fermi level and the transport states is equal to the activation energy. Empty localized states dose to the Fermi level will act as traps and give rise to a relaxation peak in the imaginary part of the dielectric permittivity.