The Meyer–Neldel rule in sol–gel derived polycrystalline ZnO:Al thin films

The present paper reports the application of Meyer–Neldel Rule to the observed spread in activation energy in electrical conduction of sol–gel derived ZnO:Al polycrystalline thin films deposited on corning 7059 glass substrate. The experimental results obtained on electrical conductivity over a wide range of temperature (150–600 K) have been analyzed in the light of theory corresponding to the two different transport paths. The conduction mechanism in the high temperature range (400–600 K) is found to be thermally activated whereas at low temperature it is attributed to variable range hopping. The variation in activation energy with Al doping concentration in ZnO has been studied in order to estimate the characteristic MNR temperature where the conductivity process is independent of the activation energy.