Crystal Structure and Ferroelectric Property of Tungsten-substituted Bi4Ti3O12 Thin Films Prepared by Metal-Organic Chemical Vapor Deposition

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W-substituted Bi4Ti3O12 (BIT), Bi4(Ti3-xWx)O12, films were prepared on (111)Pt/IrO2/SiO2/Si substrates at 600°C by metal-organic chemical vapor deposition (MOCVD). The degree of (117) orientation and the lattice spacing of 117 Bi4(Ti3-xWx)O12 increased with increasing W content up to $x=0.25$. Ferroelectricity was hardly observed in as-deposited films but confirmed in the films after annealing at 700°C. The coercive field ($E_{\text{c}}$) monotonically increased with increasing W content, but the remanent polarization ($P_{\text{r}}$) showed a maximum value at $x=0.11$. $P_{\text{r}}$ and $E_{\text{c}}$ of Bi4(Ti2.89W0.11)O12 thin film after heat treatment was 13 μC/cm2 and 160 kV/cm, respectively. W-substituted films showed high fatigue resistance against continuous switching up to $8\times 10^{10}$ cycles. These results show that W substitution for BIT film is effective in improving the ferroelectricity.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2003-05-15