The effect of the concentration and oxidation state of Sn on the structural and electrical properties of indium tin oxide nanowires

High quality single-crystalline indium tin oxide (ITO) nanowires with controlled Sn contents of up to 32.5at.% were successfully synthesized via a thermal metal co-evaporation method, based on a vapor-liquid-solid growth mode, at a substrate temperature of as low as 540 °C. The high solubility of Sn in the nanowires was explained with the existence of Sn^{2 +} ions along with Sn^{4 +} ions: the coexistence of Sn^{2 +} and Sn ^{4 +} ions facilitated their high substitutional incorporation into the In₂O₃ lattice by relaxing structural and electrical disturbances due to the differences in ionic radii and electrical charges between Sn and In^{3 +} ions. It was revealed that, while the lattice parameter of the ITO nanowires had a minimum value at a Sn content of 6.3at.%, the electrical resistivity had a minimum value of about 10 ^{- 3}Ωcm at a Sn content of 14at.%. These structural and electrical behaviors were explained by variation in the relative and total amounts of the two species, Sn^{2 +} and Sn^{4 +}.