Tunnel Current through a Thin Al2O3 Film with Nonuniform Thickness

摘要

In order to clarify the origin of the discrepancy between theoretical and experimental values of tunneling current through a thin Al2O3 layer, nonuniformity of the thickness of the oxide layer is taken into account in the determination of the theoretical current of an AlAl2O3Al thin‐film tunnel emitter. The nonuniformity mentioned above is expressed by a modified Poisson''s distribution function with respect to the oxide thickness s=nq, where q is a definite thickness unit and n is an integer. The above‐cited distribution is discontinued by some finite integer κ, by which the distribution function below a thickness s=κq is discarded so that the calculated tunneling current approaches the experimental value. Numerical calculation of the current through the oxide layer with such nonuniformity of thickness is worked out with regard to two samples prepared anodically by using an electrolyte of 3% ammonium tartrate, and the predicted voltage‐current characteristics are actually obtained. Thus, such a scheme can remove the discrepancy, at least in part, between the calculated and the measured tunneling currents.