Full Control of Polarization in Ferroelectric Thin Films Using Growth Temperature to Modulate Defects

Weymann, Christian; Fernandez‐Peña, Stéphanie; Naden, Aaron B.; Dedon, Liv R.; Martin, Lane W.; Triscone, Jean‐Marc; Paruch, Patrycja

doi:10.1002/aelm.202000852

Cited by 21 publications

(20 citation statements)

References 59 publications

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“…Thus, interface defects appear to be less effective at stabilizing the ferroelectric polarization for the whole film. It is important to note that a more complex distribution of defects than that calculated here, such as defect gradients ( 41 ), could occur in the film. More pronounced screening effects could be observed in that scenario.…”

Section: Resultsmentioning

confidence: 81%

Interface and surface stabilization of the polarization in ferroelectric thin films

Gattinoni

Strkalj

Härdi

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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Ferroelectric perovskites present a switchable spontaneous polarization and are promising energy-efficient device components for digital information storage. Full control of the ferroelectric polarization in ultrathin films of ferroelectric perovskites needs to be achieved in order to apply this class of materials in modern devices. However, ferroelectricity itself is not well understood in this nanoscale form, where interface and surface effects become particularly relevant and where loss of net polarization is often observed. In this work, we show that the precise control of the structure of the top surface and bottom interface of the thin film is crucial toward this aim. We explore the properties of thin films of the prototypical ferroelectric lead titanate (PbTiO3) on a metallic strontium ruthenate (SrRuO3) buffer using a combination of computational (density functional theory) and experimental (optical second harmonic generation) methods. We find that the polarization direction and strength are influenced by chemical and electronic processes occurring at the epitaxial interface and at the surface. The polarization is particularly sensitive to adsorbates and to surface and interface defects. These results point to the possibility of controlling the polarization direction and magnitude by engineering specific interface and surface chemistries.

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Section: Resultsmentioning

confidence: 81%

Interface and surface stabilization of the polarization in ferroelectric thin films

Gattinoni

Strkalj

Härdi

et al. 2020

Proc. Natl. Acad. Sci. U.S.A.

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“…This further opens the pathway to surface engineering of ferroelectric states. [29][30][31] However, vacancy dynamics can dominate material responses upon transition to the nanometer scale as well as in the presence of large electric fields. Hence, the open question is whether enhanced functional properties of ferroelectric materials can emerge due to the interplay between polarization instability and bulk vacancy dynamics.…”

Section: Doi: 101002/adma202106426mentioning

confidence: 99%

Oxygen Vacancy Injection as a Pathway to Enhancing Electromechanical Response in Ferroelectrics

et al. 2021

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Since their discovery in late 1940s, perovskite ferroelectric materials have become one of the central objects of condensed matter physics and materials science due to the broad spectrum of functional behaviors they exhibit, including electro‐optical phenomena and strong electromechanical coupling. In such disordered materials, the static properties of defects such as oxygen vacancies are well explored but the dynamic effects are less understood. In this work, the first observation of enhanced electromechanical response in BaTiO3 thin films is reported driven via dynamic local oxygen vacancy control in piezoresponse force microscopy (PFM). A persistence in peizoelectricity past the bulk Curie temperature and an enhanced electromechanical response due to a created internal electric field that further enhances the intrinsic electrostriction are explicitly demonstrated. The findings are supported by a series of temperature dependent band excitation PFM in ultrahigh vacuum and a combination of modeling techniques including finite element modeling, reactive force field, and density functional theory. This study shows the pivotal role that dynamics of vacancies in complex oxides can play in determining functional properties and thus provides a new route toward– achieving enhanced ferroic response with higher functional temperature windows in ferroelectrics and other ferroic materials.

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“…In line with this, a non-stoichiometric phase of Bi 2 O 3−x at the surface has been shown to cause a local polarization change in BFO films 23,24 . Similarly, cationic vacancies were reported to affect the PTO polarization orientation 25 . Furthermore, the observed time for the reconstruction of polarization (ii) of about 10 2 s matches the theoretically derived value in response to ion migration 26 .…”

Section: Resultsmentioning

confidence: 95%

In-situ monitoring of interface proximity effects in ultrathin ferroelectrics

et al. 2020

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The development of energy-efficient nanoelectronics based on ferroelectrics is hampered by a notorious polarization loss in the ultrathin regime caused by the unscreened polar discontinuity at the interfaces. So far, engineering charge screening at either the bottom or the top interface has been used to optimize the polarization state. Yet, it is expected that the combined effect of both interfaces determines the final polarization state; in fact the more so the thinner a film is. The competition and cooperation between interfaces have, however, remained unexplored so far. Taking PbTiO3 as a model system, we observe drastic differences between the influence of a single interface and the competition and cooperation of two interfaces. We investigate the impact of these configurations on the PbTiO3 polarization when the interfaces are in close proximity, during thin-film synthesis in the ultrathin limit. By tailoring the interface chemistry towards a cooperative configuration, we stabilize a robust polarization state with giant polarization enhancement. Interface cooperation hence constitutes a powerful route for engineering the polarization in thin-film ferroelectrics towards improved integrability for oxide electronics in reduced dimension.

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Full Control of Polarization in Ferroelectric Thin Films Using Growth Temperature to Modulate Defects

Cited by 21 publications

References 59 publications

Interface and surface stabilization of the polarization in ferroelectric thin films

Interface and surface stabilization of the polarization in ferroelectric thin films

Oxygen Vacancy Injection as a Pathway to Enhancing Electromechanical Response in Ferroelectrics

In-situ monitoring of interface proximity effects in ultrathin ferroelectrics

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