Electrical breakdown measurements of semicontinuous metal films

The breakdown current Ic of a percolating system is measured on real materials. We find that IcB-x, B is the weakly nonlinear response determined by third-harmonic generation. A new criterion for Ic is suggested, defined as the current at which a hot spot reaches the melting temperature of the metallic grains, Tm. This criterion remains valid in the presence of nonlinear effects. It is also consistent with the experimental observations: At Ic the resistance either increases to infinity or decreases, i.e., the local geometry is changed at Tm. Modeling the breakdown by hot spots yields the above power law with 0.5x0.36, in excellent agreement with the measured data: x=0.48 and 0.41 for Ag and Au films.