Growth of ferroelectric bismuth lanthanum nickel titanate thin filmsby rf magnetron sputtering

The epitaxial growth, structural properties, and ferroelectric properties of bismuth lanthanum nickel titanate ( Bi 1 − x La x ) ( Ni 0.5 Ti 0.5 ) O 3 (BLNT) thin films deposited on Pt ( 100 ) ∕ Mg O ( 100 ) substrates by rf magnetron sputtering have been investigated using x-ray diffraction, transmission electron microscope, and polarization-electric field hysteresis loop measurements. The ferroelectric BLNT ( 00 ℓ ) phase with c -axis orientation and a single-phase tetragonal perovskite structure appeared at x ⩾ 0.3 . The tetragonality ( c ∕ a ) increased significantly from 1.004 to 1.028 with increasing La content. The fabricated BLNT films of x ⩾ 0.3 indicated the apparent fourfold rotational symmetry observed for a MgO(202) substrate, a bottom Pt(202) electrode, and a BLNT(101) ferroelectric film, based on ϕ scan measurements. These results imply that the present La-substituted BLNT films are grown heteroepitaxially at x ⩾ 0.3 . It was confirmed that Bi in the BLNT films is in a trivalent state at A sites in the perovskite crystal, based on x-ray anomalous diffraction measurements and x-ray absorption near edge structure spectra. The sputtering technique using compacted powder targets designed by taking the bond dissociation energy of metal oxides into account provided epitaxial perovskite-structured BLNT thin films on Pt ( 100 ) ∕ Mg O ( 100 ) substrates. It is shown that the c -axis oriented epitaxial BLNT film exhibits a hysteresis loop shape with a P r value of 12 μ C ∕ cm 2 that is comparable to typical high-performance Bi 3.25 La 0.75 Ti 3 O 12 (BLT) film.