Characterization of SrxBa1−xTiO3 Pulsed Laser Deposition Thin Films

Abstract

AbstractThin films of SrTiO3 (STO) and SrxBa1−xTiO3 (SBT) with x = 0.35, 0.5, 0.9, and prepared by excimer laser deposition on LaAlO3 and MgO were studied. SEM analysis indicates that the surfaces of these films are smooth with isolated pores, except the SBT(x=0.5)/LaAlO3 sample, where a high concentration of large pores was found. X-ray diffraction (XRD) results show well oriented films. External FT-IR reflection studies reveals a band around 500 cm−x, which shows a significant frequency shift with increasing component concentration. Also, this IR-reflectivity band presents no changes between the SBT(x=0.9)/LaALO3 sample annealed at 750°C and the same film annealed at 850°C. On other hand, the STO/LaAlO3 and STO/MgO films show differences in frequency position of this reflectivity band. Raman spectra of the SBT sample with x ≥ 0.35 show broad bands associated with the BaTiO3 (BTO) material. However, all the phonons bands are broader than those in BTO, in particular the band around 309 cm−. Raman results suggest that the spectrum is a consequence of a breakdown in the translational symmetry due to defects. Raman scattering also indicates a similarity between SBT(x=0.9) at 750°C and that at 850°C. Micro-Raman and EDX analysis show that STO/MgO and SBT(x=0.35)/LaAlO3 films are close to the expected stoichiometry, while STO/LaAlO3 and SBT(x=0.9) films present deficiencies of titanium and oxygen.