The effects of excessive Bi on the structural, electrical and multiferroic properties of the La-doped Bi$_{6}$Fe$_{2}$Ti$_{3}$O$_{18}$ (Bi$_{5.25}$La$_{0.75}$Fe$_{2}$Ti$_{3}$O$_{18}$) thin films prepared on Pt(111)/Ti/SiO$_{2}$/Si(100) substrates by using a chemical solution deposition method are reported. The structures of the thin films were studied by using X-ray diffraction, Raman scattering spectroscopy and scanning electron microscopy. From the experimental comparisons, a low electrical leakage current of 1.84 $\times$ 10$^{-5}$ A/cm$^{2}$ at 100 kV/cm and enhanced ferroelectric properties, such as a large remnant polarization (2$P_{r}$) of 10.5 $\mu$C/cm$^{2}$ and a low coercive field (2$E_{c}$) of 400 kV/cm at 485 kV/cm, were observed for the 5% Bi-excess La-doped Bi$_{6}$Fe$_{2}$Ti$_{3}$O$_{18}$ thin film. The formation of a stable bismuth layer-structured phase, a lower $c$-axis orientation, an optimum crystallinity and a dense microstructure with a smooth surface morphology correlate with the improved electrical and multiferroic properties of the 5% Bi-excessive Bi$_{6}$Fe$_{2}$Ti$_{3}$O$_{18 }$ thin film.

Keywords: Aurivillius La doped Bi$_{6}$Fe$_{2}$Ti$_{3}$O$_{18}$ thin film, Chemical solution deposition, Structure, Multiferroic properties