Growth and characterization of single crystalline tin oxide (SnO2) nanowires

Single crystalline tin oxide (SnO2) nanowires have been synthesized by the carbothermal reduction of SnO2 nanopowder followed by thermal evaporation of the reduced precursor and growth via the vapor–liquid–solid (VLS) growth mechanism. The nanowires are deposited on amorphous SiO2 and single-crystalline Al2O3 and TiO2 substrates of different orientations that are coated with a thin film of gold catalyst. While the SnO2 single crystal nanowires grow randomly oriented on SiO2, they exhibit a definite epitaxial relationship for growth on lattice-matched Al2O3 and TiO2 substrates. Selective-area growth of the nanowires in specific regions of the substrates has been accomplished by lithographically patterning the Au catalyst layer. For nanowires deposited on (1 0 0) and (1 1 0)-oriented TiO2 substrates, the morphology of nanowires is sensitively dependent on the growth direction and also on the substrate-precursor distance. By using gold colloids with a narrow size distribution, instead of a thin film, monodisperse SnO2 nanowires that are well isolated have been synthesized.