Size- and surface-dependent photoresistance in SnO₂ nanowires

Nanostructured one-dimensional materials, such as nanowires, tubes and rods, are gaining increasing attention due to interesting properties and confinement effects, however controlled synthesis of these structures is still limited to a few methods. We present here the synthesis of SnO₂ nanowires (Ø, 50 - 1000 nm) at moderate temperatures (550 - 900°C) using a molecular source [Sn(OBu¹)₄] with pre-existent Sn-O bonds. The growth occurs via a catalyst driven vapor-solid-solid mechanism. Size-selective synthesis of NWs in high areal density was achieved by choosing Au particles of appropriate size. HR-TEM analysis reveals the single crystalline behaviour of wires with a preferred growth direction [100]. Use of SnO ₂ nanowires as potential optical switches for UV applications was demonstrated by the photo-response measurements. Determination of band gap values confirmed the blue-shift of the main photo-response peak with shrinking radial dimensions of the wires. Furthermore, deposition of vanadium oxide onto SnO₂ led to a red-shift of the main conduction value of the nanowires.