Structural properties of SnO2 nanowires and the effect of donor like defects on its charge distribution
SourcePhysica Status Solidi (A) Applications and Materials Science
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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. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.