Large anisotropy of ferroelectric and dielectric properties for Bi3.15Nd0.85Ti3O12 thin films deposited on Pt∕Ti∕SiO2∕Si

Polycrystalline Bi3.15Nd0.85Ti3O12 (BNdT) thin films of a-axis preferential orientation [α(100)=62%] and high c-axis orientation [α(001)=96%] were fabricated directly on Pt∕Ti∕SiO2∕Si substrates through a sol-gel process. We observed strong dependences of ferroelectric and dielectric properties on the film orientation, with a remanent polarization 2Pr of 39μC∕cm2 and dielectric constant εr of 343 at 100 kHz in the a-axis oriented film; 2Pr of 20μC∕cm2 and εr of 331 in the film of random orientation; and 2Pr of 13μC∕cm2,εr of 218 in the highly c-axis oriented film. Furthermore, the 2Pr value of a purely a-axis-oriented BNdT film can be predicted to be ∼51μC∕cm2. The large anisotropy of 2Pr and εr values demonstrates that the polarization vector of BNdT is close to the a axis.