Ferroelectricity in Strain-Free<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>SrTiO</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:math>Thin Films

Jang, Ho Won; Kumar, Amit; Denev, S.; Biegalski, Michael D.; Maksymovych, Peter; Bark, Chung Wung; Nelson, Christopher T.; Folkman, C. M.; Baek, Seung Hyub; Balke, Nina; Brooks, Charles M.; Ténné, D. A.; Schlom, D. G.; Chen, Lei; Pan, Xiaoqing; Kalinin, Sergei V.; Gopalan, Venkatraman; Eom, C. B.

doi:10.1103/physrevlett.104.197601

Cited by 254 publications

(148 citation statements)

References 34 publications

(39 reference statements)

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“…Biaxial strain of SrTiO 3 templates tensile strain to produce a [110] (in-plane) polarization. Experimental evidence suggests a more complex picture, with many strain-states resulting in a relaxor behavior at room temperature (11,22) (23,24), synchrotron radiation X-ray scattering (25,26), and tunneling (27), indicate that in strain-free SrTiO 3 a few unit cells near the LaAlO 3 interface have ferroelectric-like structural distortions with local polarization pointing away from the interface, and decreasing in magnitude with distance from the interface (28). Biaxial compressive strain induces a tetragonal distortion along 001, which would enhance this polarization, potentially uniformly polarizing the SrTiO 3 throughout its thickness (29).…”

Section: Resultsmentioning

confidence: 99%

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Tailoring a two-dimensional electron gas at the LaAlO ₃ /SrTiO ₃ (001) interface by epitaxial strain

Bark

Felker

Wang

et al. 2011

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

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148

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Recently a metallic state was discovered at the interface between insulating oxides, most notably LaAlO 3 and SrTiO 3 . Properties of this two-dimensional electron gas (2DEG) have attracted significant interest due to its potential applications in nanoelectronics. Control over this carrier density and mobility of the 2DEG is essential for applications of these unique systems, and may be achieved by epitaxial strain. However, despite the rich nature of strain effects on oxide materials properties, such as ferroelectricity, magnetism, and superconductivity, the relationship between the strain and electrical properties of the 2DEG at the LaAlO 3 ∕SrTiO 3 heterointerface remains largely unexplored. Here, we use different lattice constant single-crystal substrates to produce LaAlO 3 ∕SrTiO 3 interfaces with controlled levels of biaxial epitaxial strain. We have found that tensile-strained SrTiO 3 destroys the conducting 2DEG, while compressively strained SrTiO 3 retains the 2DEG, but with a carrier concentration reduced in comparison to the unstrained LaAlO 3 ∕SrTiO 3 interface. We have also found that the critical LaAlO 3 overlayer thickness for 2DEG formation increases with SrTiO 3 compressive strain. Our first-principles calculations suggest that a strain-induced electric polarization in the SrTiO 3 layer is responsible for this behavior. The polarization is directed away from the interface and hence creates a negative polarization charge opposing that of the polar LaAlO 3 layer. This behavior both increases the critical thickness of the LaAlO 3 layer, and reduces carrier concentration above the critical thickness, in agreement with our experimental results. Our findings suggest that epitaxial strain can be used to tailor 2DEGs properties of the LaAlO 3 ∕SrTiO 3 heterointerface.oxide interface | electronic transport | polar discontinuity S train has been used to engineer and enhance numerous properties of materials. For example, mobility in semiconductors (1,2), and transition temperatures in ferroelectric materials (3-6), and superconductors (7) have been controlled by strain. A recently discovered two-dimensional electron gas (2DEG) at the LaAlO 3 ∕SrTiO 3 interface (8,9) has attracted great interest due to its unique application to nanoscale oxide devices (10). So far, most studies of 2DEGs at oxide interfaces were performed using TiO 2 -terminated SrTiO 3 bulk single-crystal substrates. Despite the rich nature of strain effects on oxide materials properties, the relationship between the strain and electrical properties of the 2DEG at the LaAlO 3 ∕SrTiO 3 heterointerface remains largely unexplored.One important effect of strain arises from the constraint that integrating 2DEGs to other functional devices or substrates always involves strain. Understanding the effect of strain on a 2DEG at the LaAlO 3 ∕SrTiO 3 interface is essential for these considerations. In addition, incorporation of strain might lead to unique functional properties. For example, strain can induce an electric polarization in otherwise nonpol...

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Section: Resultsmentioning

confidence: 99%

“…In addition, incorporation of strain might lead to unique functional properties. For example, strain can induce an electric polarization in otherwise nonpolar SrTiO 3 (11). It has been predicted that polarization can be used to control 2DEG properties at oxide heterointerfaces (12,13).…”

mentioning

confidence: 99%

Tailoring a two-dimensional electron gas at the LaAlO ₃ /SrTiO ₃ (001) interface by epitaxial strain

Bark

Felker

Wang

et al. 2011

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

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235

148

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“…The macroscopic properties of ferroelectric and piezoelectric materials that make them appealing for current and future technologies can be more fully understood and improved through detailed knowledge of their domain structures at the nanoscale and mesoscale (11)(12)(13)(14)(15).…”

mentioning

confidence: 99%

Charge gradient microscopy

Hong

Tong

Park

et al. 2014

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

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Here we present a simple and fast method to reliably image polarization charges using charge gradient microscopy (CGM). We collected the current from the grounded CGM probe while scanning a periodically poled lithium niobate single crystal and single-crystal LiTaO 3 thin film on the Cr electrode. We observed current signals at the domains and domain walls originating from the displacement current and the relocation or removal of surface charges, which enabled us to visualize the ferroelectric domains at a scan frequency above 78 Hz over 10 μm. We envision that CGM can be used in high-speed ferroelectric domain imaging and piezoelectric energyharvesting devices.screen charge | atomic force microscopy | piezoresponse | charge scraping

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“…SrTiO 3 is a commonly used ferroelectric at microwave frequencies [20,22,23]. In this work, the parameters of SrTiO 3 are chosen to be T C = 42 K, Θ F = 175 K, ξ S = 0.018, 00 = 2081, E N = 19.3 kV/cm, α = 2 × 10 9 m −1 [20].…”

Section: Permittivity Of Ferroelectric Materialsmentioning

confidence: 99%

Microwave Tunable Metasurfaces Implemented With Ferroelectric Materials and Periodical Copper Wires

Yeh¹,

Kiang²

2014

PIER M

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Abstract-A tunable metasurface composed of multiple resonant units is proposed, with each unit containing a block of SrTiO 3 ferroelectric and a periodical copper-wire structure. The local transmission coefficient of the metasurface can be controlled by tuning the permittivity of SrTiO 3 via a bias voltage. A tunable metasurface is simulated to steer the beam direction at the angles of 30 • and 14.47 • , respectively. Another one is simulated to focus the wave beam at the focal lengths of 2λ 0 and 4λ 0 , respectively.

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Ferroelectricity in Strain-FreeSrTiO3Thin Films

Cited by 254 publications

References 34 publications

Tailoring a two-dimensional electron gas at the LaAlO ₃ /SrTiO ₃ (001) interface by epitaxial strain

Tailoring a two-dimensional electron gas at the LaAlO ₃ /SrTiO ₃ (001) interface by epitaxial strain

Charge gradient microscopy

Microwave Tunable Metasurfaces Implemented With Ferroelectric Materials and Periodical Copper Wires

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Ferroelectricity in Strain-FreeSrTiO3Thin Films

Cited by 254 publications

References 34 publications

Tailoring a two-dimensional electron gas at the LaAlO 3 /SrTiO 3 (001) interface by epitaxial strain

Tailoring a two-dimensional electron gas at the LaAlO 3 /SrTiO 3 (001) interface by epitaxial strain

Charge gradient microscopy

Microwave Tunable Metasurfaces Implemented With Ferroelectric Materials and Periodical Copper Wires

Contact Info

Product

Resources

About

Tailoring a two-dimensional electron gas at the LaAlO ₃ /SrTiO ₃ (001) interface by epitaxial strain

Tailoring a two-dimensional electron gas at the LaAlO ₃ /SrTiO ₃ (001) interface by epitaxial strain