Effect of interphase boundaries on resistivity and thermopower of nanocrystalline Re-Si thin film composites

The phase formation, electrical resistivity, and thermoelectric power of the thin film Re-Si composites have been investigated at different stages of the transformation from the amorphous to nanocrystalline state. The nanocrystallization was achieved by the annealing of amorphous films with the initial composition Re0.34Si0.66, which is equal to the composition of the crystalline ReSi2 semiconductor. The composite films include only two phases: the amorphous phase and the nanocrystalline ReSi2 with the mean grain size of about 10 nm; however, a large volume fraction of the composite films is occupied by interfaces and intergrain regions. The transport properties of this semiconductor-semiconductor system show nonmonotonic dependence on the volume fraction of the nanocrystalline phase. The role of the interfaces in this peculiar behavior is discussed. [S0163-1829(98)02636-8].