The temperature-controlled growth of In₂O₃ nanowires, nanotowers and ultra-long layered nanorods

Indium oxide (In₂O₃) nanowires (with diameters of 25-90 nm and lengths of 10-50 νm), nanotowers (with diameters 100-150 nm and lengths below 10 νm) and long layered nanorods (with diameters of 200-400 nm and lengths of 20-50 νm) are grown through carbothermal reduction of In ₂O₃ powder by varying the source temperature in a CVD horizontal furnace. At 875 °C source temperature, In₂O ₃ nanowires were formed by a VLS (vapor-liquid-solid) mechanism. The growth is changed to VS (vapor-solid)-initiated growth on the substrate surface when the source temperature is raised to 950 °C due to high saturation vapor pressure. Meanwhile, alternate VLS-VS grown nanotowers can be obtained at the bottom of the substrates. Growth of one-dimensional nanostructures with different structures and variation in growth mechanism from a single precursor with the confinement of vapor pressure enables the diversity of In ₂O₃ nanostructure synthesis. The morphologies and crystalline structures are characterized by x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopy (HRTEM). The growth mechanisms of these structures are discussed.