Surface passivation and conversion of SnO2 to SnS2 nanowires

SnO2 nanowires have been grown on Si(0 0 1) via the vapour-liquid-solid mechanism at 800 °C and then exposed to H2S between 300 and 600 °C. The SnS2/SnO2 nanowires obtained at 300 °C consist of tetragonal rutile SnO2 and hexagonal SnS2, exhibited defect related photoluminescence at 2.4 eV and have smaller resistances than the SnO2 nanowires. We show how the Fermi level pinning at the surface of a SnS2/SnO2 nanowire would lead to an increase of the one dimensional electron gas density, smaller barrier height and resistance. The SnO2 nanowires are fully converted into hexagonal SnS2 at 400 °C resulting into photoluminescence at 2.4 and 2.8 eV but have considerably larger resistances than the SnO2 nanowires which are eliminated and converted into SnS2 crystals above 400 °C.