Raman scattering and growth disorders in single as-grown TiO2 nanowires

An oxidation procedure has been developed to grow single-crystalline TiO(2) nanowires of the pure rutile phase, allowing subsequent characterizations of SEM, XRD, Raman, and TEM without any post-growth preparations. TEM observations support that the 1D anisotropic growth is dominated by oriented attachment processes, leading to typical growth-induced defects in the nanowires. Spatial variations of the rutile E(g) and A(1g) Raman modes were unambiguously revealed on single nanowires while scanned along the growth direction parallel to the rutile [110]. Symmetry-sensitive deviations were identified by comparing the Raman data with the spatial correlation model calculations based on realistic dispersion relations of the rutile, reflecting morphology-correlated defect distributions along single nanowires. This work provides an efficient, non-destructive in situ characterization approach for guiding growth design in future nanotechnology.