Influence of Precursor Chemistry on Morphology and Composition of CVD-Grown SnO2 Nanowires

Tin oxide (SnO2) nanowires (NWs) were synthesized via the gold-catalyzed chemical vapor deposition of tin(IV) and tin(II) precursors, namely, [Sn((OBu)-Bu-t)(4)] (1) and [Sn((OBu)-Bu-t)(2)](2) (2). Nanowires were deposited on gold-coated Si(001) substrates, following the vapor-liquid-solid mechanism. Energy-dispersive X-ray (EDX) analysis and high-resolution transmission electron microscopy (HR-TEM) measurements on individual nanostructures showed that the change in tin valence from +IV to +II has significant influence on the morphology and composition of the resulting NWs. Whereas 1 led directly to the growth of SnO2 nanowires, 2 underwent a disproportionation reaction whereby the elemental phase (Sn-0) reacted with Au nanoparticles to form a Au-Sn intermetallic catalyst. Comparative analysis of gas-sensing behaviors of nanowires grown from 1 and 2 illustrated that crystallographic imperfections, such as oxygen deficiency and a change in the oxidation states of the cations, are subject to the precursor configurations (Sn:O ratio in 1 and 2) and can significantly alter the surface properties, such as transduction behavior and electronic transport, that are responsible for their sensitivity toward analyte gases.