Relaxor-Like Behavior of Pb_.5Ca_.5TiO₃ Thin Films

Abstract

Single phase thin films of ferroelectric Pb_.5Ca_.5TiO₃ were deposited onto Pt/TiO₂/ SiO₂/Si(100) substrates by spin-on sol-gel process. The films show large diffusivity in the dielectric constant variation with temperature and frequency dispersion of the temperature of the dielectric constant maxima, T_mK' . From polarization—temperature measurements, remnant polarization persists well above the dielectric constant maximum (close to 297 K). These all properties are characteristics of relaxor ferroelectrics as previously proposed in the literature for Pb_.5Ca_.5TiO₃ bulk ceramics, reported for first time as thin films. The Vogel-Fulchner relation is fulfilled for the frequency dependence of the temperature of the maximum of dielectric constant, T_mK'. As usually detected in thin films, diffusivity of the dielectric constant is very large, and its values lowered with respect to the bulk ceramic counterpart. Possible aplication of these films as DRAM and varactors is discussed.

Keywords:

• Thin Film
• relaxor
• ferroelectric
• dielectric

Acknowledgments

This work has been supported by the Spanish project MAT2001-1564 and CAM 07M/0084/ 2002. R. Jimenez acknowledges the support of the MCYT Ramon y Cajal contract.