X-ray diffraction and Raman scattering study of thermal-induced phase transformation in vertically aligned TiO2 nanocrystals grown on sapphire(100) via metal organic vapor deposition

Chen, C.A.; Chen, K.Y.; Huang, Y. S.; Tsai, Dah–Shyang; Tiong, K. K.; Chien, F. Z.

doi:10.1016/j.jcrysgro.2008.05.021

Cited by 7 publications

(1 citation statement)

References 36 publications

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“…Though it has been stated that the walls of the NTs consist of (101) surfaces, we find using EBSD in the present work that the nanotube walls expose (110) and possibly (100) facets. The (110) surface is not prevalent in conventional anatase NPs but has been observed in a few preparations. , For an equilibrated crystal the formation energy of the (100) surface is just slightly higher than that of the (101) surface, while formation of the (110) surface requires still higher energy . DFT calculations showed that (100)-walled nanometer-size nanowires are the most stable for anatase, while a combination of (110) and (100) walls were less stable .…”

Section: Discussionmentioning

confidence: 99%

Location of Hole and Electron Traps on Nanocrystalline Anatase TiO₂

et al. 2012

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The defect photoluminescence from TiO 2 nanoparticles in the anatase phase is reported for nanosheets which expose predominantly (001) surfaces and compared to that from conventional anatase nanoparticles which expose mostly (101) surfaces. Also reported is the weak defect photoluminescence of TiO 2 nanotubes, which we find using electron backscattered diffraction to consist of walls which expose ( 110) and ( 100) facets. The nanotubes exhibit photoluminescence that is blue-shifted and much weaker than that from conventional TiO 2 nanoparticles. Despite the preponderance of (001) surfaces in the nanosheet samples, they exhibit photoluminescence similar to that of conventional nanoparticles. We assign the broad visible photoluminescence of anatase nanoparticles to two overlapping distributions: hole trap emission associated with oxygen vacancies on (101) exposed surfaces, which peaks in the green, and a broader emission extending into the red which results from electron traps on undercoordinated titanium atoms, which are prevalent on (001) facets. The results of this study suggest how morphology of TiO 2 nanoparticles could be optimized to control the distribution and activity of surface traps. Our results also shed light on the mechanism by which the TiCl 4 surface treatment heals traps on anatase and mixed-phase TiO 2 films and reveals distinct differences in the trap-state distributions of TiO 2 nanoparticles and nanotubes. The molecular basis for electron and hole traps and their spatial separation on different facets is discussed.

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