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Structural properties of SnO2 nanowires and the effect of donor like defects on its charge distribution

Authors

  • M. Zervos,

    Corresponding author
    1. Nanostructured Materials and Devices Laboratory, Department of Mechanical and Manufacturing Engineering, School of Engineering, University of Cyprus, P.O. Box 20537, 1678 Nicosia, Cyprus
    • Phone: 00357 22894509, Fax: 00357 22895081
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  • A. Othonos,

    1. Research Center of Ultrafast Science, School of Physical Sciences, University of Cyprus, PO Box 20537, 1678 Nicosia, Cyprus
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  • D. Tsokkou,

    1. Research Center of Ultrafast Science, School of Physical Sciences, University of Cyprus, PO Box 20537, 1678 Nicosia, Cyprus
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  • J. Kioseoglou,

    1. Nanostructured Materials Microscopy Group, Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
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  • E. Pavlidou,

    1. Nanostructured Materials Microscopy Group, Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
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  • P. Komninou

    1. Nanostructured Materials Microscopy Group, Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
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Abstract

Tin oxide (SnO2) nanowires (NWs) with diameters of 50 nm, lengths up to 100 µm and a tetragonal rutile crystal structure have been grown by low pressure reactive vapour transport on 1 nm Au/Si(001). The free carrier density of the SnO2 NWs measured by THz absorption spectroscopy was found to be n = (3.3 ± 0.4) × 1016 cm−3. Based on this we have determined the one-dimensional (1D) sub-band energies, overall charge distribution and band bending via the self-consistent solution of the Poisson–Schrödinger equations in cylindrical coordinates and in the effective mass approximation. We find that a high density of 1018–1019 cm−3 donor-like defect related states is required to obtain a line density of 0.7 × 109 close to the measured value by taking the Fermi level to be situated ≈0.7 eV below the conduction band edge at the surface which gives a surface depletion shell thickness of 15 nm. We discuss the origin of the donor-like states that are energetically located in the upper half of the energy band gap as determined by ultrafast, time-resolved absorption–transmission spectroscopy.

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