Crystallographic dependence of visible-light photoactivity in epitaxial ${\text{TiO}}_{2-x}{\text{N}}_x$ anatase and rutile

Journal Article · Tue Feb 03 04:00:00 EST 2009 · Physical Review. B, Condensed Matter and Materials Physics

DOI:https://doi.org/10.1103/PhysRevB.79.085401· OSTI ID:951836

Ohsawa, Takeo; Lyubinetsky, Igor; Du, Yingge; Henderson, Michael A; Shutthanandan, V; Chambers, Scott A

Nitrogen-doped TiO₂ materials have been shown to exhibit visible-light photoactivity, but the operative mechanism(s) are not well understood. Here we use structurally and compositionally well-defined epitaxial films of TiO_2-xN_x anatase (001) and rutile (110) (x≤~0.02) to show a qualitative difference between the visible-light activities for the two polymorphs. Holes generated by visible light at N sites in anatase (001) readily diffuse to the surface and oxidize adsorbed trimethyl acetate while the same in rutile (110) remain trapped in the bulk. In light of the low doping densities that can be achieved in phase-pure material, conventional wisdom suggests that holes should be trapped at N sites in both polymorphs. Although the detailed mechanism is not yet understood, these results suggest that the hole hopping probability is much higher along the [001] direction in N-doped anatase than along the [110] direction in N-doped rutile.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 951836
• Report Number(s): PNNL-SA-62108; 35220; 19393; KC0301010
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, Journal Name: Physical Review. B, Condensed Matter and Materials Physics Journal Issue: 8 Vol. 79; ISSN 1098-0121; ISSN PRBMDO
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ANIONS
ANNEALING
BINDING ENERGY
CROSS SECTIONS
Environmental Molecular Sciences Laboratory
FLUORINE
MASS SPECTROMETERS
MOLECULAR BEAM EPITAXY
OXYGEN
PHOTOCHEMISTRY
PHOTOEMISSION
PHYSICAL PROPERTIES
QUADRUPOLES
RUTILE
SPECTROMETERS
STABILITY
SUBSTRATES
TRANSPORT
X-RAY PHOTOELECTRON SPECTROSCOPY
X-RAY SOURCES