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Influence of Al doping on morphology and electrical properties of ZnO nanorods

Pure and Al doped ZnO nanorods were prepared by a two-step chemical bath synthesis. The synthesis reposes on the deposition of a seed layer, i.e. spin coating of a thin-film of Zn solution on a silicon wafer in the first step, and on growing of the zincite nanorods (ZNRs), i.e. immersion of seed layer in an equimolar zinc nitrate and hexamethylenetetramine solution at elevated temperature for 1 h in the second step. For Al doped ZNRs the stoichiometry was adjusted by 3 at% of aluminium nitrate nonahydrate. The properties of the derived ZNRs and Al-doped-ZNRs thin-films were characterized by X-ray Diffraction (XRD), atomic force microscopy (AFM) and field emission gun scanning electron microscopy (FEG SEM) with energy dispersive X-ray spectroscopy (EDS). Structurally, the diffraction results point out to compositional differences of the nanorods as a result of the Al doping. Morphologic microscopy results are in concordance with diffraction data and additionally point out to a change in the geometry of the nanorods as a result of the Al doping. Electrical properties were examined by Kelvin probe force microscopy (KPFM) and by temperature-dependent current-voltage (I-V) measurements on Au/(Al)ZnO NR/n-Si junctions. The doping lead to an increase of conductivity of the ZnO NRs by an order of magnitude. The I-V characteristics for the pure and doped NRs follow the ohmic regime at lower voltages, while for the higher voltages the observed changes were attributed to the successful Al doping. The increase in the conductivity and shifting of the geometry of the nanorods can influence the overall electric transport properties which is a desirable behaviour in the area of photocatalysis and photovoltaics.

ZnO nanorods ; Al doping ; electrical properties

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