Si-Substituted Ultrathin Ferroelectric Films

Solid solutions between Bi 2 SiO 5 and conventional ferroelectric materials such as Bi 4 Ti 3 O 12 , SrBi 2 Ta 2 O 9 and Pb(Zr,Ti)O 3 were formed using a sol-gel spin-coating method. It was found that the crystallization temperatures of the films were lower by 150 to 200°C than those of the original ferroelectric films and that the surface of the films became very flat and smooth. Because of these excellent properties, ultrathin (13- to 25-nm-thick) ferroelectric capacitors were successfully fabricated, in which the polarization was well saturated at an applied voltage of 0.5 V. Discussion on the formation mechanism of the films is also presented.