Raman spectroscopy characterisation of oriented bundles of single-crystal rutile-phase TiO2 nanorods prepared by hydrothermal bath deposition on transparent conducting substrates

Rutile-phase TiO 2 rods prepared by hydrothermal bath deposition on F:SnO 2 are in fact bundles of single-crystal TiO 2 prismatic nanorods of ~ 4 nm diameter each. These bundles of rutile-phase TiO 2 nanorods have tetragonal morphology and are strain-free (or the strain in all the samples is the sam...

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Veröffentlicht in:Applied physics. A, Materials science & processing Materials science & processing, 2019-06, Vol.125 (6), p.1-10, Article 389
Hauptverfasser: Mbulanga, C. M., Erasmus, R. M., Urgessa, Z. N., Djiokap, S. R. Tankio, Olivier, E. J., Goosen, W. E., Botha, J. R., Betz, R.
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Sprache:eng
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Zusammenfassung:Rutile-phase TiO 2 rods prepared by hydrothermal bath deposition on F:SnO 2 are in fact bundles of single-crystal TiO 2 prismatic nanorods of ~ 4 nm diameter each. These bundles of rutile-phase TiO 2 nanorods have tetragonal morphology and are strain-free (or the strain in all the samples is the same). Bundles of TiO 2 that are oriented tetragonally with respect to the substrate’s surface, can be prepared for optimized growth times. It is observed that bundles of TiO 2 nanorods act as single entities from the point of view of the Raman spectra (and thus lattice vibrations). Single prismatic nanorods of ~ 4 nm width, as observed via TEM, appear to act as “larger” crystals to the lattice phonons once stacked together to form large oriented bundles of TiO 2 . Hence, the phonon confinement effect cannot be observed because translational symmetry is preserved at the grain boundaries of the nanorods that make each TiO 2 bundle. Moreover, an increase in the density of bundles growing preferentially in the [002] direction, perpendicular to the substrate surface, results in an unusual increase of room and low (77 K) temperature Raman band E g / A 1g intensity ratios.
ISSN:0947-8396
1432-0630
DOI:10.1007/s00339-019-2688-4