Challenges in the stoichiometric growth of polycrystalline and epitaxial PbZr0.52Ti0.48O3/La0.7Sr0.3MnO3 multiferroic heterostructures using pulsed laser deposition

High quality polycrystalline and epitaxial PbZr0.52Ti0.48O3/La0.7Sr0.3MnO3 (PZT/LSMO) multiferroic thin films were deposited on single-crystal Si (100) and SrTiO3 (STO) (100) substrates using pulsed laser deposition (PLD) technique. The deposition conditions were optimized to overcome some of the challenges during the growth of stoichiometric PZT/LSMO thin films (with LSMO as the bottom layers). The major setback of the preferential evaporation of Pb during the ablation of PZT target, which leads to the growth of non-stoichiometric, Pb-deficient PZT thin films with poor ferroelectric properties, was investigated by studying the laser-target interaction sites and intensified charge-coupled detector (ICCD) imaging of the laser-ablated plumes. X-ray studies revealed that the PZT/LSMO heterostructures deposited under the optimum conditions were highly crystalline. Atomic force microscope images showed uniform grain growth with surface roughness values as low as 1.6 nm. In- and out-of-plane magnetization measurements showed saturation of 263–310 emu/cm3 and the corresponding absence or presence of magnetic anisotropy in the PZT/LSMO heterostructures on Si and STO substrates, respectively. LSMO/PZT/LSMO capacitors showed high remnant polarizations of 25–44 μC/cm2 at coercive fields of ∼30 kV/cm. A comparative study was performed on the strained epitaxial PZT/LSMO films on STO substrates and the un-strained polycrystalline PZT/LSMO films on Si substrates.