Controlling the Polarization in Ferroelectric PZT Films via the Epitaxial Growth Conditions


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Date

2023-07-11

Publication Type

Journal Article

ETH Bibliography

yes

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Abstract

The integration of thin-film ferroelectrics with reliable properties into oxide electronics requires accomplishing deterministic polarization states. Since ferroelectricity emerges during thin-film synthesis already, it is essential to elucidate how the interplay of different growth parameters affects the polarization. Here, the polarization of fully strained Pb(Zr₀.₂Ti₀.₈)O₃ (PZT) films is accessed in situ, during epitaxial growth. Surprisingly, it is found that the orientation of the out-of-plane polarization during growth may differ from the one after growth completion and it strongly depends on the substrate temperature and the oxygen partial pressure. Increasing the growth temperature and/or the oxygen partial pressure favors a uniform downward-oriented polarization, independent of the direction of polarization during growth. Specifically, for films with an emerging upward-oriented polarization, a polarization reversal and a downward-oriented polarization after cool-down is observed. The in situ measurements obtained by optical second harmonic generation (SHG) in conjunction with ex situ piezoresponse force microscopy (PFM) and X-ray diffraction (XRD) measurements point to the temperature- and pressure-dependent formation of a charged Pb defect gradient toward the film surface as the responsible mechanism for the polarization reorientation.

Publication status

published

Editor

Book title

Volume

33 (28)

Pages / Article No.

2214849

Publisher

Wiley-VCH

Event

Edition / version

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Geographic location

Date collected

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Subject

charged point defects; epitaxy; ferroelectrics; nonlinear optics; PZT; thin films

Organisational unit

03918 - Fiebig, Manfred / Fiebig, Manfred check_circle

Notes

Funding

188414 - Multifunctional oxide electronics using natural ferroelectric superlattices (SNF)
196061 - Designing oxide electronics with light (SNF)
178825 - Dynamical processes in systems with strong electronic correlations (SNF)

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