Lattice Misfit as a Design Parameter for Enhanced Dielectric Response and Tunability in Epitaxial Barium Strontium Titanate Films

Functional and structural effects of layer periodicity in chemical solution‐deposited Pb(Zr,Ti)O3 thin films

“…8,9 While attempts to obtain homogeneous PZT compositions near the MPB have become ubiquitous both in research and industrial applications, recent work on heterogeneous compositions and film structures that traverse the MPB have shown promising enhancements to ferroelectric and piezoelectric responses in increasingly thin films. 13,14 Experimental approaches, including discrete heterolayers, graded compositions, bi-and tri-layer superlattices, and other fabrication approaches have been employed to study interactions between dissimilar phases and layers in ferroelectric thin films. Theoretical methods have predicted large dielectric and piezoelectric anomalies in heterolayered epitaxial films.…”

“…11,12,19,23 However, while functional response enhancements are often reported, the mechanisms by which such enhancements are derived are somewhat debated. 10,11,13,14,17,20,24,25 While the origins of response enhancement are perhaps multifaceted and not unequivocally elucidated, the fact remains that the overwhelming majority of these reports has concentrated on single-layer films with unique B-site cation (Zr/Ti) gradients, or unique bi-layers of rhombohedral and tetragonal compositions. 12 Work by Mangalam et al, demonstrated nearly coherent strain in PZT R/T bi-layered and graded thin films, contributing to asymmetric bias profiles in the films, thereby resulting in increased tolerance to strain relaxation and enhanced ferroelectric properties.…”

“…Theoretical methods have predicted large dielectric and piezoelectric anomalies in heterolayered epitaxial films. 13,14 Experimental approaches, including discrete heterolayers, graded compositions, bi-and tri-layer superlattices, and other fabrication approaches have been employed to study interactions between dissimilar phases and layers in ferroelectric thin films. 11,12,[14][15][16][17][18][19][20][21][22][23] The majority of these have demonstrated some degree of enhancement to ferroelectric response, in addition to interesting polarization interactions and thermodynamic properties, such as unusual phase change sequences and nonergodicity.…”

“…11 Others have suggested that electrostatic coupling, internal bias fields, interfacial asymmetry, and flexoelectricity contribute to increased polarizability and resulting enhancements of functional properties in ferroelectric superlattices. 10,11,13,14,17,20,24,25 While the origins of response enhancement are perhaps multifaceted and not unequivocally elucidated, the fact remains that the overwhelming majority of these reports has concentrated on single-layer films with unique B-site cation (Zr/Ti) gradients, or unique bi-layers of rhombohedral and tetragonal compositions.…”