Pulsed laser deposition of ferroelectric gradient thin films

This thesis explores the use of off-center pulsed laser deposition (PLD) to fabricate ferroelectric thin films with controlled gradients in thickness, stoichiometry, and strain, enabling high-throughput investigation of growth-structure-property relationships in oxides. Using BaTiO3 (BTO) and Hf0.4Zr0.6O2 (HZO) as model systems, the work examines how process parameters and heterostructure design govern film morphology, strain, and ferroelectric switching. For BTO grown on SrTiO3 (STO), systematic variation of laser fluence and oxygen pressure revealed that pressure most strongly dictates morphology, stoichiometry, and lattice parameter gradients, while sufficient fluence is required to suppress Ba-rich island formation; together, these results establish thresholds for controlling oxygen vacancy and cation ratios. Off-center growth was then extended to heterostructures combining La0.7Sr0.3MnO3 (LSMO) with HZO, where thickness gradients enabled direct observation of both constant-voltage and constant-field coercive field scaling within a single film – respectively following JKD-like behavior (n ≈ –2/3) and near thickness-invariance (n ≈ 0) – demonstrating the critical role of measurement conditions and extrinsic effects such as leakage and imprint. Finally, BTO grown on STO-buffered silicon with either LSMO or La0.07Ba0.93SnO3 (LBSO) electrodes highlighted the interplay of plume-induced strain gradients, lattice mismatch, and domain orientation in determining ferroelectric switching. While BTO/LSMO showed stable polarization with significant imprint from asymmetric electrodes, BTO/LBSO exhibited strain-engineered lattice parameters but lacked measurable out-of-plane switching, suggesting that electrode geometry must be chosen according to the domain orientation. Across these studies, off-center PLD is validated as a powerful, scalable platform for mapping intrinsic and extrinsic ferroelectric behaviors, and the work ends with a brief note on the commercialization of PLD and the search for materials that can fully exploit the advantages of this technique.