Identification of oxygen vacancy types from Raman spectra of SnO₂ nanocrystals

Abstract

Raman spectra acquired from spherical SnO 2 nanocrystals prepared by pulsed laser ablation and hydrothermal synthesis exhibit three oxygen-vacancy-related Raman modes at 234, 573, and 618 cm À1 . The peak location and intensity vary with annealing temperature under O 2 finally approaching those of bulk materials. Density functional calculation discloses that the three Raman modes stem from subbridging, in-plane, and bridging oxygen vacancies, respectively. Raman spectra can thus be used to discern different types of oxygen vacancies in SnO 2 nanocrystals.

Mesopororous Sn0.9−xIn0.1Cux(I)O2−δ gas sensors with selectivity to H2S working under humid air conditions

“…Our Raman results confirm that bridging oxygen vacancies are the origin of downshift in the A1g mode, as recently claimed by Liu et al[22].…”

“…Four vibrational modes are Raman active: three non-degenerated, A1g, B1g, B2g, and a doubly degenerate Eg, in all these active Raman modes the oxygen atoms vibrate while Sn atoms are at rest [20,21]. Therefore, disorder in the oxygen sublattice and nanoparticle size strongly influence the vibrational properties of this material [21,22]. RS of all the samples (Fig.…”

“…There is a significant peak shifting of A1 g towards lower wavenumbers: 626 cm À1 in SIC1, 624 cm À1 in SIC2 and 622 cm À1 in SIC3. The phonon confinement effect can explain a wavenumber shift of the A1g mode down to 628 cm À1 -compared to A1g $ 638 cm À1 in cassiterite (SnO 2 ) -when the nanocrystal size decreases to 5.5 nm [22]. Therefore, it can be inferred that the size change is Fig.…”

“…The region 400-600 cm À1 is dominated by broads bands centered at $480-500 and 540 cm À1 . These bands are disorder activated modes and arise from the presence of oxygen vacancies in the nanocrystallites [22]. They have been described in nanocrystalline SnO 2 for particle sizes smaller than 10 nm, considered as the surface disorder-activated component of the spectra due to the contribution of atoms situated at the several atomic layers in the surface [21].…”

Optical and magnetic properties of (Er, F) co-doped SnO$_{2}$ nanocrystals

“…For comparison, the Raman spectrum of Er-doped SnO 2 is also presented in Figure 5a. nanocrystals might arise from deeper OVs [37]. The interaction of Er 3+ /F − ions in the SnO 2 lattice created changes in the vibrational modes, which are reflected in the disappeared and/or reduced Raman intensity [38].…”