Deposition of Bi4-xNdxTi3O12 films with direct liquid injection metallorganic chemical vapor deposition and characterization of ferroelectric properties

Abstract

Using Bi(tmhd)(3), Nd(tmhd)(3) and Ti((OC3H7)-C-i)(2)(tmhd)(2) (tmhd: 2,2,6,6-tetramethyl-3,5-heptanedione), Bi4-xNdxTi3O12 (BNT) thin films were prepared on Pt(111)/Al2O3/SiO2/Si substrates by direct liquid injection metallorganic chemical vapor deposition (DLI-MOCVD). The composition of BNT film was dependent on the deposition temperature and the concentration of the mixture solution. Also, the film composition could be controlled by adjusting the concentration of Bi and Nd precursors in the solution through the competitive substitution of Bi and Nd element in the Bi site of Bi-layer perovskite structure (Bi4Ti3O12). BNT films deposited at 450 degrees C (Bi-4-xNdxTi3O12 with x = 0.89) had (117) orientation, and crystallinity of this BNT film was improved with annealing. The remanent polarization value (2P(r)) of Bi4-xNdxTi3O12 (x = 0.89) film deposited at 450 degrees C and annealed at 650 degrees C for 60 min in an O-2 atmosphere was 29 mu C/cm(2) at the applied voltage of 5 V. BNT capacitors did not show any significant fatigue up to 4 x 10(10) cycles at a frequency of 1 MHz. Bi4-xNdxTi3O12 (x = 0.89) films with DLI-MOCVD showed good properties for nonvolatile ferroelectric random access memory. (c) 2006 The Electrochemical Society.