Fabrication of SnO2 Nanowire Networks on a Spherical Sn Surface by Thermal Oxidation

SnO2 nanowire networks were synthesized in two steps. Sn spheres (30-800 nm in diameter) embedded in SiO2 on a Si substrate was synthesized by a chemical vapor deposition method at 700A degrees C. Using the source of these Sn spheres, SnO2 nanowire (20-40 nm in diameter; 1-10 mu m in length) networks on a spherical Sn surface were synthesized by a thermal oxidation method at 800A degrees C through the support of gold. Field emission scanning electron microscopy and high-resolution transmission electron microscopy images indicated that SnO2 nanowires are single crystalline. In addition, the SnO2 nanowire is also a tetragonal rutile, with the preferred growth directions along [100] and a lattice spacing of 0.237 nm. Subsequently, the NO2 sensing properties of the SnO2 network nanowires sensor at an operating temperature of 50-250A degrees C were examined, and showed a reversible response to NO2 at various NO2 concentrations. Finally, a possible formation mechanism of Sn spheres and SnO2 nanowire networks is also discussed.