TiO₂ anatase intermediary layer acting as template for ZnO pulsed electrodeposition

Highlights: • First report on the use of a TiO₂ intermediate layer for the growth n-type ZnO nanorod arrays by pulsed electrodeposition. • Importantly, films are compared to those grown without a TiO₂ intermediate layer but with the same ZnO seed layer. • In this case results show that nanorod density increases 3-fold to ~ 165μm⁻² and nanorod diameter decreases by 50% to ~ 40nm. • Results also show that green intra-bandgap photoluminescence emission is suppressed indicating enhanced crystalline quality. Zinc oxide nanorod (ZnO NR) films for photocatalytic and energy conversion applications were synthesized by pulsed electrodeposition. The films were prepared on modified fluorine-doped tin oxide (FTO) glass coated with thin layers of ZnO seeds and porous anatase titanium dioxide (TiO₂). The ZnO seed layers were prepared electrochemically, whilst the TiO₂ layers by spin-coating. Morphological and structural analysis of the films reveal the effect of the TiO₂ intermediate layers on ZnO NRs was to improve vertical alignment, increase spatial density and decrease diameter. Room temperature photoluminescence (PL) results show that the ZnO NRs exhibit near band edge recombination and deep level emission in the green and red spectral regions. The green emission was almost suppressed for ZnO NRs grown using the TiO₂ intermediate layer followed by two step electrodeposition of ZnO. The prepared films demonstrated photoelectrochemical behaviour in aqueous electrolytes. Additionally, the ZnO NRs prepared with a TiO₂ intermediate layer demonstrated increased stability to photo-dissolution.