Noise in mono- and polycrystalline aluminum

The (Formula presented) noise in three types of aluminum lines has been investigated in the temperature range 140-510 K. The types are one long single crystal, a chain of short single crystals (“bamboo”), and a polycrystal. In the lines of the first two types the (Formula presented) noise power is significantly lower than in the polycrystalline specimens. The temperature dependence of the noise power in the polycrystalline lines shows a plateau between 370 and 415 K, corresponding to activation energies 0.9-1.0 eV. Both types of monocrystalline lines have equal noise power with a peak around 340 K, corresponding to an activation energy of about 0.8 eV. In the polycrystalline lines the dominant contribution to (Formula presented) noise appears to be the thermally activated motion of atoms in grain boundaries. The measurements on the monocrystalline lines reveal the existence of at least one further contribution to (Formula presented) noise in metals, presumably associated with the thermally activated diffusion of atoms along dislocations.