THE ROLE OF MICROGEOMETRY IN THE ELECTRICAL BREAKDOWN OF METAL-INSULATOR MIXTURES

Abstract

The breakdown phenomena of percolative metal-insulator composites and their extreme sensitivity to fine details of the microgeometry are discussed, for three different cases: the critical current of superconductor-insulator mixtures (or superconductor-normal metal); the dielectric breakdown of metal-insulator composites below the percolation threshold (insulating regime); and the electrical breakdown above the metal-insulator transition (metallic regime). Two experimental techniques for characterizing the microgeometry are described: (a) 1/f noise measurements, which provide the fourth moment of the current distribution; (b) the harmonic generation method, where the weakly nonlinear electrical response due to local Joule heating provides information on the fourth (and higher) moment of the current distribution.