Current noise measurements in continuous metal thin films

Current noise phenomena were investigated in pure Al thin films. Noise measurements were performed on very small sample volumes (less than 10−11 cm3) obtained by electromigration damaging of the film, at current densities higher than 106 A/cm2 with an apparatus whose sensitivity was of the order of 10−19 V2/Hz. Under these conditions, which probably provide the best sensitivity limit at present available, no excess noise was detected before the destruction of the sample, except for occasional instabilities corresponding to macroscopic structural changes of the film. It is concluded that a stationary current noise cannot be observed in a metal conductor within the highest sensitivities presently attainable.