Large remanent polarization of (Bi,Nd)4Ti3O12 epitaxial thin films grown by metalorganic chemical vapor deposition

(104)-oriented Bi4Ti3O12, La-substituted Bi4Ti3O12[(Bi3.44La0.56)Ti3O12] and Nd-substituted Bi4Ti3O12[(Bi3.54Nd0.46)Ti3O12] films were epitaxially grown on (111)SrRuO3//(111)SrTiO3 substrates at 700 degreesC by metalorganic chemical vapor deposition. All deposited films showed strong (104) orientations. The values of the remanent polarization (P-r) and coercive field (E-c) of the (104)-oriented epitaxial (Bi3.54Nd0.46)Ti3O12 thin film were 25 muC/cm(2) and 135 kV/cm, respectively. This P-r value was larger than that of the (104)-oriented (Bi3.44La0.56)Ti3O12 film: P-r and E-c values of the (Bi3.44La0.56)Ti3O12 were 17 muC/cm(2) and 145 kV/cm, respectively. These good ferroelectric properties of (Bi3.54Nd0.46)Ti3O12 films can be explained by a large tilting of TiO6 octahedra induced by the substitution of Nd3+, the ionic radius of which is smaller than that of La3+. Moreover, this P-r value is almost equal to that of commercially used lead zirconate titanate (PZT) films for nonvolatile ferroelectric random access memory (FeRAM) applications. These (104)-oriented epitaxial (Bi3.54Nd0.46)Ti3O12 thin films also showed a fatigue-free character. As a result, lead-free Nd-substituted Bi4Ti3O12 films with good ferroelectric properties comparable with those of PZT films are useful candidates for FeRAM applications. (C) 2002 American Institute of Physics.