Thermal-assisted field emission

The central problem in the study of ionic conduction is to discover the details of the atomic transport processes involved in the growth of films. This will be discussed in the first part of this review. The electronic conductivity is of considerable theoretical interest and is of great practical importance for microelectronic devices. We discuss the system in which a thin metal counterelectrode replaces the electrolyte solution in which the oxide was made. Thermionic and field assisted emission, tunneling processes, impurity band conduction, and space-charge limited currents, have to be considered. We shall draw on results for oxide films made by other processes, such as evaporation and thermally promoted reaction with oxygen. 

We now turn attention to conditions at the electrodes. These play vital roles in establishing the pre-breakdown conditions in the liquid under high electric stress and in triggering the breakdown itself. It has been natural to invoke electron injection at the cathode as an important component since high fields will lower the potential barrier to electron transfer across the interface whether it occurs by a thermally activated or tunnelling process. However, employment of the Schottky formula for field-assisted thermionic emission or the Fowler-Nordheim one for tunnel emission which are appropriately applicable only for electron transfer to a vacuum is a much too simplified solution to the problem. 

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