We report the results of a three-step deposition process for realisation of uniform arrays of ZnO nanorods, involving chemical bath deposition of aligned seed layers followed by nanorod nucleation sites and subsequent vapour phase transport growth of nanorods. This process combines chemical bath deposition techniques, which enable substrate independent seeding and nucleation site generation with vapour phase transport growth of high crystalline and optical quality ZnO nanorod arrays. Our data indicate that the three-step process produces uniform nanorod arrays with narrow and rather monodisperse rod diameters (centred at ~ 70 nm) across substrates of centimetre dimensions. X-ray photoelectron spectroscopy, scanning electron microscopy and x-ray diffraction were used to study the growth mechanism and characterise the nanostructures.

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1 Introduction High mobility semiconductors are envisaged to replace silicon as the channel material in future generations of metal-oxide-semiconductor field effect transistors (MOSFETs) based on the industrial roadmap for semiconductor devices [1,2], coupled with the incorporation of high-κ dielectric materials [3]. However, a major roadblock to this is the presence of significant levels of interface defects between the III-V and high-κ materials, which are known to cause frequency dispersion and Fermi level pinning in semiconductor devices. As a result, the identification, prevention or removal of these interface states is of critical importance to the future development of the technology. In 0.53 Ga 0.47 As is one of the proposed high mobility semiconductor materials under investigation [4], having an electron mobility significantly greater than that of silicon, as well as being lattice matched to InP, which has potential implications for the facile formation of buried channel quantum well structures [5] and through substrate engineering, the potential to be grown on a silicon platform [6]. The use of atomic hydrogen (AH) as a method for oxide removal and surface cleaning of III -V semiconductors has been proposed due to the relatively low temperature needed to instigate the oxide removal [7,8], which is important due to the low decomposition temperature of III-V

Photoluminescence (PL) studies of the surface exciton peak in ZnO nanostructures at ∼3.367 eV are reported to elucidate the nature and origin of the emission and its relationship to nanostructure morphology. Localised voltage application in high vacuum and different gas atmospheres show a consistent PL variation (and recovery), allowing an association of the PL to a bound excitonic transition at the ZnO surface modified by an adsorbate. Studies of samples treated by plasma and of samples exposed to UV light under high vacuum conditions show no consistent effects on the surface exciton peak indicating no involvement of oxygen species. X-ray photoelectron spectroscopy data indicate involvement of adsorbed OH species. The relationship of the surface exciton peak to the nanostructure morphology is discussed in light of x-ray diffraction, scanning and transmission electron microscopy data.