title: A two-dimensional phase of TiO₂ with a reduced bandgap.
abstract: Titanium dioxide is the prototypical transition metal oxide photocatalyst. However, the larger than 3 eV bandgap of common bulk phases of TiO₂ limits its light absorption to UV light, making it inefficient for solar energy conversion. Attempts at increasing visible light activity by narrowing the bandgap of TiO₂ through doping have proven difficult, because of defect-induced charge trapping and recombination sites of photo-excited charge carriers. Here, we report the existence of a dopant-free, pure TiO₂ phase with a narrow bandgap. This new pure TiO₂ phase forms on the surface of rutile TiO₂(011) by oxidation of bulk titanium interstitials. We measure a bandgap of only ~2.1 eV for this new phase, matching it closely with the energy of visible light.
authors: Department of Physics, University of South Florida, Tampa, Florida 33620, USA.
authors: Junguang
authors: J
authors: Tao
authors: Tim
authors: T
authors: Luttrell
authors: Matthias
authors: M
authors: Batzill
mesh_terms: D055598:Chemical Phenomena; D003460:Crystallization; D004583:Electrons; D016252:Microscopy, Scanning Tunneling; D010084:Oxidation-Reduction; D044367:Phase Transition; D055668:Photochemical Processes; D056951:Photoelectron Spectroscopy; D013057:Spectrum Analysis / Q000379:methods; D013499:Surface Properties; D013816:Thermodynamics; D014025:Titanium / Q000737:chemistry*
chemical_list: C009495:titanium dioxide; D014025:Titanium