Large Remanent Polarization in Sm-Substituted BiFeO3 Thin Film Formed by Chemical Solution Deposition

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Bi1-xSmxFeO3 ($x=0--0.15$) (BSFO) thin films were formed on Pt/Ti/SiO2/Si(100) substrates by chemical solution deposition. The spin-coated, dried, and prefired thin films were finally crystallized at 500 °C in air and in N2. It was found that Sm-substitution for Bi in BiFeO3 increased the grain size and the leakage current density. The optimal concentration for improving remanent polarization ($P_{\text{r}}$) was characterized to be 5 at. %. In 10 and 15 at. % BSFO films, incorporation of Sm atoms was found to be excess, leading to degradation of ferroelectric properties. The $P_{\text{r}}$ and coercive electric field values in 5 at. % BSFO film measured at electric field of 1.5 MV/cm and frequency of 25 kHz were 82 μC/cm2 and 0.35 MV/cm, respectively. In addition, the minimal coercive electric voltage of 7.5 V was achieved in a 126-nm-thick 7.5 at. % Sm-substituted BFO film.
2010-04-25