First-Principles Study of Titania Nanoribbons: Formation, Energetics, and Electronic Properties

Abstract

The geometric, electronic, and magnetic properties of titania nanoribbons (TiO 2 NRs) are investigated with use of first-principles calculations within density-functional theory. The TiO 2 NRs formed by cutting ultrathin TiO 2 nanosheet along armchair and zigzag axes have high energetic stability. Zigzag TiO 2 NRs are more preferable than armchair ones. The electronic structures of TiO 2 NRs highly depend on the growth orientation and the ribbon width. Introducing oxygen vacancy defects into the edges of zigzag TiO 2 NRs under poor oxygen conditions can reduce the band gap and trigger the spin-polarization of edge states. These TiO 2 NRs with well-defined atomic structures, high stability, and tunable electronic properties are expected to have potential applications in solar cells, spintronic devices, and sensors.

Structure, Synthesis, and Applications of TiO2 Nanobelts

“…The band structure of TiO 2 nanobelts is not only affected by their diameter, but also by their surface physical and chemical properties, and their growth orientation . Different growth orientations result in different facet terminations, i.e, terminated with Ti or O atoms.…”

“…1D TiO 2 nanostructures usually display thickness‐dependent bandgaps . When the thickness of the TiO 2 nanobelt is less than 2.5 nm, the bandgap is enlarged to a value above that of bulk anatase and bulk rutile TiO 2 , because of quantum confinement effects arising with the decrease in thickness of the nanobelt ( Figure a) . However, in general, thicker TiO 2 nanobelts are produced, and are therefore usually characterized by bandgaps narrower than the 3.4 eV theoretically predicted for the 2.5 nm TiO 2 nanobelts.…”

“…The bandgaps are fitted to the formula E g = a + b / W , where the fitting parameters a and b are 3.49 and 0.82 eV Å for ATiO 2 NRs with even N A ; 3.49 and –2.07 eV Å for ATiO 2 NRs with odd N A ; 3.62 and 1.23 eV Å for ZTiO 2 NRs with even N z ; and 3.62 and ­–1.68 eV Å for ZTiO 2 NRs with odd N z . Reproduced with permission . Copyright 2010, ACS.…”

“…The energy at the Fermi level ( E F ) is set to zero. Reproduced with permission . Copyright 2010, ACS.…”

Electronic structure and optical properties of Ag-doped SnO2 nanoribbons

“…This phenomenon is similar to TiO 2 nanoribbons. 18 Compared with the band gap of pure SnO 2 nanosheet (2.59 eV) 30 which we calculated with generalized gradient approximation (GGA), there are 0.31 and 0.4 eV decrement for ZSnO 2 NRs and ASnO 2 NRs respectively.…”