Crystallographic Dependence of Visible-light Photoactivity in Epitaxial TiO_2-xN_x Anatase and Rutile

Journal Article · Tue Feb 03 04:00:00 EST 2009 · Physical Review. B, Condensed Matter and Materials Physics, 79(8):Article number: 085401

DOI:https://doi.org/10.1103/PhysRevB.79.085401· OSTI ID:963826

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)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 963826
• Report Number(s): PNNL-SA-59944; KC0301010
• Journal Information: Physical Review. B, Condensed Matter and Materials Physics, 79(8):Article number: 085401, Journal Name: Physical Review. B, Condensed Matter and Materials Physics, 79(8):Article number: 085401 Journal Issue: 8 Vol. 79
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
DOPED MATERIALS
EPITAXY
HOLES
MASS TRANSFER
NITROGEN
OXIDATION
TITANIUM OXIDES
VISIBLE RADIATION
hopping conduction
organic compounds
photochemistry
semiconductor doping
semiconductor epitaxial layers
semiconductor materials
titanium compounds