Structural and optical investigation of BaTiO ₃ nanostructures produced from TiO ₂ nanorod arrays using hydrothermal method

A well-aligned single-crystalline barium titanate (BaTiO 3 ) nanostructured layer was prepared by the growth and conversion of vertically aligned TiO 2 nanorods. This was achieved through a two-step hydrothermal method on fluorine-doped tin oxide (FTO)-coated glass substrates via the dissolution-nucleation-recrystallization mechanism. The morphology, crystal structure and optical properties were investigated using field-emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), X-ray diffraction (XRD), Raman spectroscopy, photoluminescence (PL) and Z-scan techniques. The X-ray and selected area diffraction patterns (SAED) confirmed the formation of the aligned single-crystalline tetragonal BaTiO 3 layer. The room temperature Raman spectrum showed the tetragonal TiO 2 -related vibrational modes in BaTiO 3 . The PL spectra indicated the coalescence of band edge emissions of BaTiO 3 and TiO 2 in the blue and visible regions of the investigated spectra. The Z-scan experiments performed using the CW Nd:YAG laser revealed a positive nonlinear refractive index on the order of 10[Formula: see text] cm 2 W[Formula: see text], indicating the self-focusing type of cation in the BaTiO 3 sample. The nonlinear absorption coefficient of the BaTiO 3 nanostructures in the order of 10[Formula: see text] cm W[Formula: see text] was also calculated. As expected, the BaTiO 3 nanostructure synthesized in this study is a good candidate for use in nonlinear optics.