Regensburg 2019 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 24: Thin Film Properties: Structure, Morphology and Composition (XRD, TEM, XPS, SIMS, RBS, AFM, ...) Part I
DS 24.8: Vortrag
Donnerstag, 4. April 2019, 17:00–17:15, H39
Controlling defect distribution and intrinsic domain structure in ultrathin ferroelectric films — •Christian Weymann1, Céline Lichtensteiger1, Stéphanie Fernandez-Peña1, Liv Dedon2, Lane Martin2, Aaron Naden3, Amit Kumar3, Jean-Marc Triscone1, and Patrycja Paruch1 — 1DQMP, University of Geneva — 2MSE, UC Berkley — 3SMP, QU Belfast
Domains significantly affect the properties of ultrathin ferroelectric films. Controlling the domain structure is thus crucial for applications, and of great fundamental interest. It results from the interplay of the depolarizing field, destabilizing the uniform polarization configuration, and of any built-in field favoring one polarization direction. The former must be compensated by screening to maintain a uniform polarization configuration. The latter results from an asymmetry in this screening or from internal sources, such as charged defect dipoles.
We show that we can manipulate both these fields, acting on the screening of the bound charge using dielectric spacer layers, or modulating the built-in field and defect distribution through changes in the growth temperature of PbTiO3 thin films, allowing full control over the intrinsic polarization state. Combining PFM mapping of the domain structure, RBS to quantify differences in defect density and distribution, and XRD measurements of the strain profile in the films, we propose a defect-dipole gradient mechanism to explain the observed results, in agreement with Ginzburg-Landau-Devonshire modeling. We also take advantage of this unique control over the domain structure to investigate the microstructure of the domains themselves.