Role of dual-laser ablation in controlling the Pb depletion in epitaxial growth of Pb(Zr0.52Ti0.48)O3 thin films with enhanced surface quality and ferroelectric properties

Abstract

Pb depletion in Pb(Zr0.52Ti0.48)O3 (PZT) thin films has remained as a major setback in the growth of defect-free PZT thin films by pulsed laser ablation techniques. At low excimer (KrF) laser fluences, the high volatility of Pb in PZT leads to non-congruent target ablation and, consequently, non-stoichiometric films, whereas, at high laser fluences, the inherent ejection of molten droplets from the target leads to particulate laden films, which is undesirable in heterostructure growth. To overcome these issues, a dual-laser ablation (PLDDL) process that combines an excimer (KrF) laser and CO2 laser pulses was used to grow epitaxial PZT films on SrTiO3 (100) and MgO (100) substrates. Intensified-charge-coupled-detector (ICCD) images and optical emission spectroscopy of the laser-ablated plumes in PLDDL revealed a broader angular expansion and enhanced excitation of the ablated species as compared to those for single-laser ablation (PLDSL). This led to the growth of particulate-free PZT films with higher Pb content, better crystallinity, and lower surface roughness as compared to those deposited using PLDSL. For FE measurements, PZT capacitors were fabricated in situ using the latticed-matched metallic oxide, La0.7Sr0.3MnO3, as the top and bottom electrodes. PZT films deposited using PLDDL exhibited enhanced polarization for all driving voltages as compared to those deposited using PLDSL. A highest remanent polarization (Pr) of ∼91 μC/cm2 and low coercive field of ∼40 kV/cm was recorded at 9 V driving voltage. Fatigue characterization revealed that PZT films deposited using PLDDL showed unchanging polarization, even after 109 switching cycles.

Controlled Ti Seed Layer Assisted Growth and Field Emission Properties of Pb(Zr0.52Ti0.48)O3 Nanowire Arrays

“…Ferroelectric (FE) perovskite oxides continue to be an important class of materials because of their high dielectric and piezoelectric coefficients and switchable nonvolatile polarization properties. − Among the state-of-the-art perovskite oxide materials, lead zirconium titanate with the specific composition of Pb(Zr 0.52 Ti 0.48 )O 3 (PZT) exhibits the highest piezo and ferro-coefficients and is of great technological interest for applications as piezoelectric transducers, pyroelectric sensors, high-dielectric capacitors, and nonvolatile memory devices. − Most frequently, PZT is used in the form of single crystals, polycrystalline bulk ceramics, and thin films in microelectronics devices ,, and in miniaturized FE random access memory (FRAM) devices. − …”