title: Oxygen vacancy density-dependent transformation from infrared to Raman active vibration mode in SnO2 nanostructures.
abstract: Raman spectra acquired from spherical, cubic, and cuboid SnO2 nanocrystals (NCs) reveal a morphologically independent Raman mode at ∼302 cm(-1). The frequency of this mode is slightly affected by the NC size, but the intensity increases obviously with decreasing NC size. By considering the dipole changes induced by oxygen vacancies and derivation based on the density functional theory and phonon confinement model, an oxygen vacancy density larger than 6% is shown to be responsible for the transformation of the IR to Raman active vibration mode, and the intensity enhancement is due to strong phonon confinement.
authors: National Laboratory of Solid State Microstructures, Nanjing University, Nanjing 210093, China.
authors: T H
authors: TH
authors: Li
authors: L Z
authors: LZ
authors: Liu
authors: X X
authors: XX
authors: Li
authors: X L
authors: XL
authors: Wu
authors: H T
authors: HT
authors: Chen
authors: Paul K
authors: PK
authors: Chu