Fabrication of Nb-doped bismuth titanate thin films using nonionic block copolymer: Enhanced ferroelectric properties

Crack-free Nb-doped Bi4Ti3O12 (Nb-BIT-p) ferroelectric thin films were fabricated utilizing nonionic block copolymer, HO(CH2CH2O)20(CH(CH3)CH2O)70(CH2CH2O)20H (EO20PO70EO20), on Pt/Ti/SiO2/Si substrates by a processing route of metalorganic solution deposition. The Nb-BIT-p films after calcination showed only a Bi4Ti3O12-type crystalline phase with a random orientation and small grains (< 0.4 μm). The remanent polarization (2Pr) and the coercive field (Ec) values of Nb-BIT-p capacitors were unusually high, such as 42 ± 3 μC/cm2 and 72 ± 5 kV/cm, respectively, at a maximum applied field of 160 kV/cm. After 1.5 × 1010 read/write cycles with ± 8 V amplitude (160 kV/cm) at 1 MHz frequency, the 2Pr value was partially reduced, but recoverable close to the original one by repeated switching at a high field.