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

Abstract

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 ${\mathrm{Re}}_{0.34}{\mathrm{Si}}_{0.66},$ which is equal to the composition of the crystalline ${\mathrm{ReSi}}_{2}$ semiconductor. The composite films include only two phases: the amorphous phase and the nanocrystalline ${\mathrm{ReSi}}_{2}$ 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.