A comparative study of microstructure of RuO₂ nanorods via Raman scattering and field emission scanning electron microscopy

Raman scattering (RS) and field emission scanning electron microscopy (FESEM) have been used to extract microstructural information of RuO₂ nanorods (NRs) and a two-phase system comprising NRs embedded in polycrystalline matrix deposited on different substrates by the metal-organic chemical vapor deposition method. The red shifts and asymmetric broadening of the Raman line shape for the NRs are analyzed by the spatial correlation model. The deduced spatial correlation length l is found to be much smaller than that of the average size L₀ estimated from the FESEM images. The Raman features for the two-phase system can be resolved into two parts: a Lorentzian line shape feature corresponding to the polycrystallite at higher frequency side and an asymmetrically broadened NRs' signature located at lower frequency end. The volume fraction of NRs in the two-phase system can be determined from the analysis. These results demonstrate the significance of RS as a structural characterization method when used in conjunction with FESEM.