31 October 2001 Phonon confinement and optical properties in nanosized titanium dioxide by Raman spectroscopy
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Raman spectroscopy is used to study phonon confinement effect and photoluminescence (PL) for titanium dioxide nanocrystals. A chemical solution process was developed to prepare TiO2 nanocrystals with particle sizes of 6.8 - 27.9 nm. As the grain size decreases, the lowest-frequency Eg mode at 152 cm-1 shows blueshift and broadening. The frequency shift and line width broadening were theoretically studied at different grain sizes of 6.8, 10.3 and 27.9 nm under phonon confinement model, showing good agreement with experimental results. Non-stoichiometry effect was recorded by redshift of the 422 cm-1 Eg mode, libration mode of the oxygen atoms along the c-axis. PL spectrum of the anatase TiO2 nanocrystals was recorded at exciting power as low as 0.06 W/cm2. A power-law relationship IPL approximately equals P(gamma ) was obtained between PL intensity and the excitation power. PL mechanism for TiO2 nanocrystals is attributed to the recombination via the localized levels within the forbidden gap of defect-related centers, which reside in the surface region of TiO2 nanocrystals.
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Ming-Sheng Zhang, Weifeng Zhang, Zhen Yin, "Phonon confinement and optical properties in nanosized titanium dioxide by Raman spectroscopy", Proc. SPIE 4469, Raman Spectroscopy and Light Scattering Technologies in Materials Science, (31 October 2001); doi: 10.1117/12.447377; https://doi.org/10.1117/12.447377

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