Enhancement of optical absorption by modulation of the oxygen flow of TiO2 films deposited by reactive sputtering
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Otros documentos de la autoría: Beltran, Armando; Pereira, André L. J.; Lisboa Filho, Paulo N.; Acuña, Javier; Brandt, Iuri S.; Pasa, André A.
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Mostrar el registro completo del ítemcomunitat-uji-handle:10234/9
comunitat-uji-handle2:10234/7013
comunitat-uji-handle3:10234/8638
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Título
Enhancement of optical absorption by modulation of the oxygen flow of TiO2 films deposited by reactive sputteringAutoría
Fecha de publicación
2012Editor
American Institute of Physics (AIP)ISSN
0021-8979; 1089-7550Cita bibliográfica
J. Appl. Phys. 111, 113513 (2012)Tipo de documento
info:eu-repo/semantics/articleVersión de la editorial
http://scitation.aip.org/getpdf/servlet/GetPDFServlet?filetype=pdf&id=JAPIAU0001 ...Versión
info:eu-repo/semantics/publishedVersionResumen
Oxygen-deficient TiO2
films with enhanced visible and near-infrared optical absorption have been
deposited by reactive sputtering using a planar diode radio frequency magnetron configuration. It is
observed that the ... [+]
Oxygen-deficient TiO2
films with enhanced visible and near-infrared optical absorption have been
deposited by reactive sputtering using a planar diode radio frequency magnetron configuration. It is
observed that the increase in the absorption coefficient is more effective when the O2 gas supply is
periodically interrupted rather than by a decrease of the partial O2 gas pressure in the deposition
plasma. The optical absorption coefficient at 1.5 eV increases from about 1 102
cm 1
to more than
4 103
cm 1
as a result of the gas flow discontinuity. A red-shift of 0.24 eV in the optical
absorption edge is also observed. High resolution transmission electron microscopy with
composition analysis shows that the films present a dense columnar morphology, with estimated
mean column width of 40 nm. Moreover, the interruptions of the O2 gas flow do not produce
detectable variations in the film composition along its growing direction. X-ray diffraction and
micro-Raman experiments indicate the presence of the TiO2
anatase, rutile, and brookite phases.
The anatase phase is dominant, with a slight increment of the rutile and brookite phases in films
deposited under discontinued O2 gas flow. The increase of optical absorption in the visible and
near-infrared regions has been attributed to a high density of defects in the TiO2
films, which is
consistent with density functional theory calculations that place oxygen-related vacancy states in the
upper third of the optical bandgap. The electronic structure calculation results, along with the
adopted deposition method and experimental data, have been used to propose a mechanism to
explain the formation of the observed oxygen-related defects in TiO2 thin films. The observed
increase in sub-bandgap absorption and the modeling of the corresponding changes in the electronic
structure are potentially useful concerning the optimization of efficiency of the photocatalytic
activity and the magnetic doping of TiO2
films. [-]
Publicado en
Journal of Applied Physics, num. 111Derechos de acceso
Copyright 2012 American Institute of Physics
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