Distribution function of transparencies of highly compressed disordered dielectric layers
Specific features of electron tunneling through disordered nanoscale dielectric layers are studied theoretically. Analytical expressions for transport characteristics of metal-insulator-metal contacts with an inhomogeneous dielectric layer as well as universal relations describing the distribution of the probability of the charge transfer across a disordered system of potential barriers are obtained. Two limiting cases, narrow and high barriers with abrupt boundaries and relatively broad and low barriers, which may be described by the quasiclassical approximation, have been analyzed. Although the two distribution functions are described by different analytical expressions, there is no qualitative difference between them since both functions are bimodal with a large number of strongly reflected “closed” channels, and at the same time a significant amount of “open” channels with the transmission coefficient near unity. To determine definitely the physical nature of the potential barriers, we propose to study Josephson superconductor-insulator-superconductor junctions and to extract two quantities from their current-voltage characteristic, namely, the critical supercurrent at zero voltage bias and the excess current, i.e., the constant shift of a superconducting current-voltage curve towards that measured in the normal state. Finally, high-pressure induced changes of the transparency distribution functions for an amorphous dielectric layer are foreseen.