Epitaxially Oriented Sn:In2O3 Nanowires Grown by the Vapor–Liquid–Solid Mechanism on m-, r-, a-Al2O3 as Scaffolds for Nanostructured Solar Cells

We have grown highly directional, epitaxial Sn: In2O3 nanowires via the vapor liquid solid mechanism on m-, r- and a-Al2O3 between 800°C and 900°C at 1 mbar. The Sn: In2O3 nanowires have the cubic crystal structure and are tapered with lengths up to 80 µm but they are inclined at φ ≈ 60 ° along one direction on m-Al 2O3 while those on r-Al 2O3 are inclined at φ ≈ 45 ° and oriented along two mutually orthogonal directions. In contrast vertical Sn: In2O3 nanowires were obtained on a-Al 2O3. We obtain an excellent uniformity and reproducible growth of Sn: In2O3 nanowires up to 15 mm x 15 mm on m- and r-Al2O3 which is important for the fabrication of nanowire solar cells. All of the Sn: In2O3 had a resistivity of 10 -4 Ωcm and carrier densities of the order of 1021 cm-3 in which case the charge distribution has a maximum at the surface of the Sn: In2O3 nanowires due to the occupancy of sub-bands residing well below the Fermi level as shown via the self-consistent solution of the Poisson-Schrodinger equations ...