Large tetragonality and room temperature ferroelectricity in compressively strained CaTiO3 thin films

Ryan C. Haislmaier, Yanfu Lu, Jason Lapano, Hua Zhou, Nasim Alem, Susan B. Sinnott, Roman Engel-Herbert, Venkatraman Gopalan

Research output: Contribution to journalArticle

Abstract

Ferroelectricity and piezoelectricity are desirable for a variety of higherature applications such as actuators and sensors in heat engines, higherature manufacturing, and space technologies; however, the material candidates are currently limited. Here, we demonstrate that CaTiO3, the prototype perovskite mineral, abundantly found in the Earth, which as a nonpolar material in bulk form, becomes a higherature ferroelectric oxide under compressive strain when grown as a thin film. A strain-phaseerature diagram of CaTiO3 films is created by growing films on various substrates with different in plane strains in order to map out the polar behavior for compressive and tensile strain. Using temperature dependent optical second harmonic generation analysis, we show that tensile strained films exhibit predominantly in-plane polarization with orthorhombiclike point group symmetry with a phase transition below room temperature. On the other hand, compressively strained CaTiO3 films exhibit a near-tetragonal unit cell with a c/a ratio of 1.03, larger than that of classic ferroelectric, e.g., BaTiO3 (c/a ∼1.01). These films exhibit a robust and switchable out-of-plane polarization at room temperature, with a ferroelectric transition temperature up to ∼800 K. Density functional theory calculations reveal that compressive strain gives rise to a large out-of-plane displacement of Ti-cations inside the TiO6 octahedral cages and is the major contributor to the calculated polarization of ∼9 μC/cm2. Given that nearly half of the perovskites exhibit the bulk symmetry of CaTiO3, compressive strain tuning of this perovskite family may prove to be a fertile ground for the discovery of strain-induced piezoelectrics and ferroelectrics at higheratures.

Original languageEnglish (US)
Article number051104
JournalAPL Materials
Volume7
Issue number5
DOIs
StatePublished - May 1 2019

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Ferroelectricity
Thin films
Ferroelectric materials
Polarization
Perovskite
Temperature
Point groups
Heat engines
Piezoelectricity
Tensile strain
Crystal symmetry
Film growth
Harmonic generation
Oxides
Superconducting transition temperature
Density functional theory
Minerals
perovskite
Cations
Actuators

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Engineering(all)

Cite this

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title = "Large tetragonality and room temperature ferroelectricity in compressively strained CaTiO3 thin films",
abstract = "Ferroelectricity and piezoelectricity are desirable for a variety of higherature applications such as actuators and sensors in heat engines, higherature manufacturing, and space technologies; however, the material candidates are currently limited. Here, we demonstrate that CaTiO3, the prototype perovskite mineral, abundantly found in the Earth, which as a nonpolar material in bulk form, becomes a higherature ferroelectric oxide under compressive strain when grown as a thin film. A strain-phaseerature diagram of CaTiO3 films is created by growing films on various substrates with different in plane strains in order to map out the polar behavior for compressive and tensile strain. Using temperature dependent optical second harmonic generation analysis, we show that tensile strained films exhibit predominantly in-plane polarization with orthorhombiclike point group symmetry with a phase transition below room temperature. On the other hand, compressively strained CaTiO3 films exhibit a near-tetragonal unit cell with a c/a ratio of 1.03, larger than that of classic ferroelectric, e.g., BaTiO3 (c/a ∼1.01). These films exhibit a robust and switchable out-of-plane polarization at room temperature, with a ferroelectric transition temperature up to ∼800 K. Density functional theory calculations reveal that compressive strain gives rise to a large out-of-plane displacement of Ti-cations inside the TiO6 octahedral cages and is the major contributor to the calculated polarization of ∼9 μC/cm2. Given that nearly half of the perovskites exhibit the bulk symmetry of CaTiO3, compressive strain tuning of this perovskite family may prove to be a fertile ground for the discovery of strain-induced piezoelectrics and ferroelectrics at higheratures.",
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Large tetragonality and room temperature ferroelectricity in compressively strained CaTiO3 thin films. / Haislmaier, Ryan C.; Lu, Yanfu; Lapano, Jason; Zhou, Hua; Alem, Nasim; Sinnott, Susan B.; Engel-Herbert, Roman; Gopalan, Venkatraman.

In: APL Materials, Vol. 7, No. 5, 051104, 01.05.2019.

Research output: Contribution to journalArticle

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AB - Ferroelectricity and piezoelectricity are desirable for a variety of higherature applications such as actuators and sensors in heat engines, higherature manufacturing, and space technologies; however, the material candidates are currently limited. Here, we demonstrate that CaTiO3, the prototype perovskite mineral, abundantly found in the Earth, which as a nonpolar material in bulk form, becomes a higherature ferroelectric oxide under compressive strain when grown as a thin film. A strain-phaseerature diagram of CaTiO3 films is created by growing films on various substrates with different in plane strains in order to map out the polar behavior for compressive and tensile strain. Using temperature dependent optical second harmonic generation analysis, we show that tensile strained films exhibit predominantly in-plane polarization with orthorhombiclike point group symmetry with a phase transition below room temperature. On the other hand, compressively strained CaTiO3 films exhibit a near-tetragonal unit cell with a c/a ratio of 1.03, larger than that of classic ferroelectric, e.g., BaTiO3 (c/a ∼1.01). These films exhibit a robust and switchable out-of-plane polarization at room temperature, with a ferroelectric transition temperature up to ∼800 K. Density functional theory calculations reveal that compressive strain gives rise to a large out-of-plane displacement of Ti-cations inside the TiO6 octahedral cages and is the major contributor to the calculated polarization of ∼9 μC/cm2. Given that nearly half of the perovskites exhibit the bulk symmetry of CaTiO3, compressive strain tuning of this perovskite family may prove to be a fertile ground for the discovery of strain-induced piezoelectrics and ferroelectrics at higheratures.

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