Controlled synthesis of tin-doped indium oxide (ITO) nanowires

• High-quality, vertically aligned ITO nanowires were synthesized by a thermal evaporation method.
• Although nanowire diameters depend on the size of Au catalyst, nanowire diameters are consistently larger than the size of Au catalyst that is used to grow them.
• O2 partial pressure needs to remain below 3.23 mTorr for successful nanowire growth.

Because of their high optical transparency and high electrical conductivity, ITO nanowires have been used in solar cells, diodes, and sensors. Synthesizing ITO nanowires reliably with controllable and reproducible structures and morphologies is desirable for many applications. However, the dependence of ITO nanowire structure and morphology on growth conditions has yet to be investigated systematically. In this work, experimental conditions including catalyst diameter, growth time, temperature, and oxygen partial pressure are varied to determine their impact on the diameter, length, and microstructure of synthesized nanowires. The diameters of the nanowires depend on the diameter of Au catalysts, however, not as directly as other studies have observed. Nanowire diameters of 99 nm were obtained when using 14 nm Au nanoclusters compared to 366 nm when using 321 nm Au nanoclusters. Nanowire length and diameters are independent of O2 partial pressure. However, the O2 partial pressure had to remain below 3.23 mTorr for successful nanowire growth. The optimal temperature for nanowire growth was 750 °C.