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Defect Photoluminescence of TiO2 Nanotubes

Published online by Cambridge University Press:  01 February 2011

Jeanne Louise McHale  and
Candy C. Mercado
Jeanne Louise McHale
Affiliation:
jmchale@wsu.edu, Washington State University, Chemistry, Box 644630, Pullman, Washington, 99164-4630, United States, 509 335 4063, 509 335 8867
Candy C. Mercado
Affiliation:
candy_mercado@wsu.edu, Washington State University, Materials Science Program and Department of Chemistry, Pullman, Washington, United States
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Abstract

Photoluminescence (PL) spectroscopy of nanocrystalline TiO2 using ultraviolet light excitation reveals a range of intra-bandgap defect states which emit at visible wavelengths. In this study we use 350 nm excitation to probe the luminescent defect states of TiO2 nanotubes fabricated by anodization of titanium. The nanotubes show a broad visible luminescence from 450 to 700 nm with a peak at 520-550 nm or 2.4-2.3 eV. The intensity of nanotube PL is orders of magnitude lower than that of nanoparticulate anatase and P25 (mixed-phase anatase/rutile) films of comparable thickness. Similar to the PL of the nanoparticles, the nanotube PL is increased by vacuum annealing. The nature of the nanotube defects is investigated through shifts in the intensity and shape of the PL spectra in hole or electron scavenging environments. We find the PL intensity of the nanotubes to be less dependent on environment than that of conventional TiO2 nanoparticles. We conclude that there are two inter-related reasons for decreased intensity and decreased environmental dependence of PL from TiO2 nanotubes as compared to nanoparticles: decreased density of defect states and improved carrier transport.

Keywords

defectsnanostructureelectronic structure
Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 1268: Symposium EE – Defects in Inorganic Photovoltaic Materials , 2010 , 1268-EE03-10
Copyright
Copyright © Materials Research Society 2010

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