Electronic Current Flow Through Ideal Dielectric Films

Abstract

During the past few decades a large literature has accumulated on the subject of current flow through dielectric films. Much of this material contains detailed analyses of many physical effects and a great deal of multiparameter curve fitting. Until recently all this activity had given the field a rather bad name, since it appeared that all effects were very complicated and nothing could be understood in a first-principles way. It is true, in fact, that in many thin-film systems the current flow is dominated by impurities, trapping processes, and so on, so that no simple, clear picture emerges for the mechanism of current flow. However, in the past few years it has become clear that certain insulating materials behave in a nearly ideal fashion and can be understood in a very simple and fundamental way. In this chapter I shall not attempt to discuss the mass of literature dealing with data on dielectrics that were not well characterized and well understood. Instead, I shall concentrate on examples in which nearly ideal behavior was observed and in which the simple physics of the current-flow processes is clear. In retrospect it seems obvious that much of the previous data is also understandable on rather simple grounds and that there were a number of conceptual errors that led to the belief that vastly complicated processes were involved. This is by no means true for all the data in the literature, but certainly with good hindsight resulting from a clear understanding of ideal materials, a much better understanding of the nonideal cases is also possible. Since the details of all the results I shall cite are available in the published literature, I shall discuss only the ideas and basic principles involved and give references where a more complete discussion may be found.