Since SrRuO3 (SRO) is often chosen as the lower electrode for the BFO thin film as well as for the buffer layer to control its nanoscale
domain architecture , it is desirable to investigate the optical properties of the BFO thin film grown on SRO. Spectroscopic ellipsometry (SE) is a widely used optical characterization method for materials and related systems at the nanoscale. It is based on the measuring the change in the polarization state of a linearly polarized light reflected from a sample surface which consists of Ψ, the amplitude ratio of reflected p-polarized light to s-polarized light and Δ, the phase shift difference between the both . The obtained ellipsometry spectra (Ψ and Δ at measured wavelength range) are fitted to the optical model for thin film nanostructure, and thus, rich information including surface roughness, film thickness, and optical constants of nanomaterials are revealed [13, 14]. QNZ Since Compound C solubility dmso SE allows various characterizations of the material, our group has studied some thin-film nanostructure using SE methods [15–18]. In this paper, we report the optical properties of epitaxial BFO thin film grown on SRO-buffered STO substrate prepared by pulsed-laser deposition (PLD) and measured by SE. The dielectric functions of STO, SRO, and BFO are extracted from the ellipsometric spectra,
respectively. And the optical constants of the BFO thin film are obtained. The bandgap of 2.68 eV for the BFO thin film is also received and is compared to that for BFO thin film deposited on different substrate as well as BFO single crystals. Methods The epitaxial BFO thin film was deposited
by PLD on SRO-buffered (111) STO single-crystal substrate. The SRO buffer layer was directly deposited on the STO substrate by PLD in advance. More details about the deposition PR 171 process can be taken elsewhere . The crystal phases in the as-grown BFO thin film were identified by X-ray diffraction (XRD, Bruker X-ray Diffractometer D8, Madison, WI, USA). The surface morphologies of the BFO thin film were investigated by atomic force microscopy (AFM, Veeco Instruments Inc., Atomic Force Microscope System VT-1000, Plainview, NY, USA). Both XRD and AFM investigation are employed to show growth quality of the BFO thin film for further optical find more measurement and analysis. SE measurements were taken to investigate the optical properties of the BFO film. Considering the optical investigation with respect to a substrate/buffer layer/film structure, we should firstly obtain the optical response of the STO substrate and SRO buffer layer and then research the optical properties of the BFO thin film. The ellipsometric spectra (Ψ and Δ) were collected for the STO substrate, the SRO buffer layer, and the BFO film, respectively, at an incidence angle of 75° in the photon energy range of 1.55 to 5.