Epitaxially Oriented Sn:In2O3 Nanowires Grown by the Vapor–Liquid–Solid Mechanism on m-, r-, a-Al2O3 as Scaffolds for Nanostructured Solar Cells
Date
2019Author
Charalampous, AndreasZervos, Matthew
Kioseoglou, Joseph
Tsagaraki, Katerina
Androulidaki, Maria
Konstantinidis, George
Tanasă, Eugenia
Vasile, Eugeniu
Source
ACS Applied Energy MaterialsVolume
2Issue
6Pages
4274-4283Google Scholar check
Metadata
Show full item recordAbstract
We have grown highly directional, epitaxial Sn:In2O3 nanowires via the vapor–liquid–solid mechanism on m-, r- and a-Al2O3 between 800 and 900 °C at 1 mbar. The Sn:In2O3 nanowires have the cubic bixbyite crystal structure and are tapered with lengths of up to 80 μm, but they are inclined at ϕ ≈ 60° along one direction on m-Al2O3 while those on r-Al2O3 are inclined at ϕ ≈ 45° and oriented along two mutually orthogonal directions. In contrast, vertical Sn:In2O3 nanowires were obtained on a-Al2O3. We obtain excellent uniformity and reproducible growth of Sn:In2O3 nanowires up to 15 mm × 15 mm on m- and r-Al2O3, which is important for the fabrication of nanowire solar cells. All of the Sn:In2O3 nanowires had a resistivity of 10–4 Ω cm and carrier densities on the order of 1021 cm–3, in which case the charge distribution has a maximum at the surface of the Sn:In2O3 nanowires as a result of the occupancy of sub-bands residing well below the Fermi level, as shown via the self-consistent solution of the Poisson–Schrödinger equations in the effective mass approximation. We also show that the Sn:In2O3 nanowires are capable of light emission and exhibited room-temperature photoluminescence at 3.1 eV as a result of band-to-band radiative transitions but also at 2.25 eV as a result of donor-like states residing energetically in the upper half of the energy band gap. We discuss the advantages of using ordered networks of Sn:In2O3 nanowires in solar cell devices and issues pertaining to their fabrication.