Sol-gel derived strontium barium niobate films: Structural, optical and electrical properties

Sol-gel derived SrxBa1-xNb2O6 thick and thin films have been successfully fabricated on various substrates and characterized.; Thick films of Sr0.6Ba0.4Nb2O6 (SBN60) and Sr0.75Ba0.25Nb2O 6 (SBN75) up to 4 mum thick were fabricated on Si. The effect of self template layer ensured preferential orientation, that was revealed by Raman spectroscopy and X-ray diffraction (XRD). Columnar growth was observed in cross-sectional scanning electron microscopy (SEM). Surface morphology was studied with atomic force microscopy (AFM) and r.m.s. roughnes values were measured to be < 10 nm.; Epitaxial SBN60 films were fabricated on MgO and (La0.5Sr 0.5)CoO3/MgO (LSCO/MgO) substrates. An innovative technique of pulsed laser deposition was adopted, in which a layer of PLD derived SBN60 film acted as the self template layer for the subsequent coating of sol-gel derived SBN films. The structural and morphological properties of these dual-process-prepared films were studied again with XRD, SEM and AFM. Improved epitaxy was shown.; The relationship between film thickness and annealing temperature was further studied. A set of thin SBN films of two-layer thickness were fabricated. They had a range of compositions, namely SBN25, SBN30, SBN40, SBN50, SBN60 and SBN70, and annealing temperatures from 200 to 700°C. It was found that their behaviours fell into two groups. SBN with x ≤ 0.5 attained maximum thickness at the annealing temperature of 600°C, but for x>0.5, maximum thickness was obtained at 700°C. The process of crystallization was monitored through observation of their top views and cross sections, which indicated that the onset of crystallization in either groups was between 500°C and 600°C.; Optical properties of SBN60 films were investigated with spectral elipsometry1 (SE), as functions of annealing temperature (200 to 700°C) and annealing durations (0.5 to 10 h). A triple-layer Lorentz model was adopted in the analysis of the measured SE spectra. The results reveal that the refractive indices of SBN60 films increased significantly near the crystallization temperature of the films. Their extinction coefficients also showed a similar trend being zero for amorphous films and rising to large values around 0.1 at 2.5 eV in films annealed at > 600°C. A similar dependence applied for annealing duration. Both facts demonstrate the significant influence of crystallization on refractive index and extinction coefficient.