Oxide superlattices with alternating<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>p</mml:mi></mml:math>and<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mi>n</mml:mi></mml:math>interfaces

Bristowe, Nicholas C.; Artacho, Emilio; Littlewood, P. B.

doi:10.1103/physrevb.80.045425

Cited by 72 publications

(105 citation statements)

References 38 publications

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“…38 Although, we do note that recent theoretical models of the LaAlO 3 /SrTiO 3 system point to the possibility of ferroelectric-like distortions in the LaAlO 3 layer as well. 2,39,40 In accord with previous observations however, 38 we suspect an interface dipole in SrTiO 3 , which in turn suggests that the electron gas lies not exactly at the interface, but burried one or a few monolayers within the SrTiO 3 . We thus speculate that the large influx of charge carriers into the potential well at the onset of Zener tunneling changes the local electric field and modifies the dipole strength, causing the observed hysteretic behaviour in CV .…”

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confidence: 76%

Built-in and induced polarization across LaAlO3/SrTiO3 heterojunctions

et al. 2010

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Ionic crystals terminated at oppositely charged polar surfaces are inherently unstable and expected to undergo surface reconstructions to maintain electrostatic stability. Essentially, an electric field that arises between oppositely charged atomic planes gives rise to a built-in potential that diverges with thickness. Here we present evidence of such a built-in potential across polar LaAlO3 thin films grown on SrTiO3 substrates, a system well known for the electron gas that forms at the interface. By performing tunneling measurements between the electron gas and metallic electrodes on LaAlO3 we measure a built-in electric field across LaAlO3 of 80.1 meV/Å. Additionally, capacitance measurements reveal the presence of an induced dipole moment across the heterostructure. We forsee use of the ionic built-in potential as an additional tuning parameter in both existing and novel device architectures, especially as atomic control of oxide interfaces gains widespread momentum.As dictated by Maxwell's equations, the accumulation of screening charges at the boundary between dissimilar materials is one means 1 of ensuring a continuous electric displacement at the interface. 2 For instance, a layer of trapped screening charge forms the two dimensional electron gas that compensates a polarization mismatch at gallium nitride 3 and zinc oxide 4 based heterostructure interfaces. In insulating oxides, charge accumulation was observed at the interface between SrTiO 3 substrates with atomically precise surfaces and polar LaAlO 3 films. 5 LaAlO 3 thin films grown on singly terminated SrTiO 3 surfaces 6 comprise negatively charged AlO 2 and positively charged LaO end planes and are polar in the ionic limit. 1,7,8 When at least four unit cells (u.c.) of LaAlO 3 are deposited on TiO 2 terminated SrTiO 3 , an electron gas forms near the interface in SrTiO 3 . 5,9,10 It is often hypothesized that at a thickness of four u.c. the potential across LaAlO 3 exceeds the band gap of SrTiO 3 and electrons tunnel from the valence band of LaAlO 3 to the SrTiO 3 potential well, completely diminishing the potential across LaAlO 3 . 11 Thus within this picture, in the presence of an electron gas no field would be expected across the LaAlO 3 . However, if all the charge carriers do not lie precisely at the interface or have an extrinsic (oxygen vacancies 12 or cation doping 13 ) origin, the LaAlO 3 potential will not be fully screened and can thus be probed. 14 Alternatively, the precise band alignment between the LaAlO 3 and SrTiO 3 will also determine the strength of the residual fields in the LaAlO 3 . 15 Addressing this issue by determining the existence of an uncompensated built-in potential in LaAlO 3 is central to understanding the true nature of the polar LaAlO 3 /SrTiO 3 interface.We probe the potential landscape across the LaAlO 3 and the interface region in SrTiO 3 by employing a typical metal-insulator-metal capacitor geometry such that the LaAlO 3 thin films form the dielectric layer sandwiched between evaporated metallic electrodes an...

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confidence: 76%

Built-in and induced polarization across LaAlO3/SrTiO3 heterojunctions

et al. 2010

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“…By increasing the thickness of the CoFe 2 O 4 and MgAl 2 O 4 layers, we can expect that the buildup potential leads to a "polar catastrophe" phenomenon similar to that found in the LaAlO 3 /SrTiO 3 (001) superlattices [38]. According to the schematic view displayed in Fig.…”

Section: Details Of the Calculationsmentioning

confidence: 99%

Fully spin-polarized two-dimensional electron gas at the <span class="aps-inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML"><msub><mrow><mi mathvariant="normal">CoFe</mi></mrow><mn>2</mn></msub><msub><mrow><mi mathvariant="normal">O</mi></mrow><mn>4</mn></msub><mo>/</mo><msub><mrow><mi mathvariant="normal">MgAl</mi></mrow><mn>2</mn>

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2014

Phys. Rev. B

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We performed first-principles calculations to show that a fully spin-polarized two-dimensional electron gas can be created at the interface between the polar and insulating spinel oxides CoFe 2 O 4 and MgAl 2 O 4 . We give a clear description of the physical parameters (in particular the atomic termination of the interfaces), which favor the formation of this electron gas that is due either to an electric field induced in stoichiometric oxide layers because of their polar character or to a charge reorganization that preserves the global electric neutrality in nonstoichiometric layers. We show that the electric field-induced spin-polarized two-dimensional electron gas can only exist if the thickness of the CoFe 2 O 4 layer is large enough and that it may be destroyed by intermixing at the interfaces.

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“…Also in the LaAlO 3 /SrTiO 3 system an induced polarization in SrTiO 3 and a reduction of the band gap with thickness of the polar layer was observed. 22 Finally, it is interesting to look at the structural aspects of the interfaces. Here we analyze the intermixed case, but similar features are found in the sharp interfaces, too.…”

Section: Interfacesmentioning

confidence: 99%

First-principles study of intermixing and polarization at the DyScO3/SrTiO3interface

et al. 2012

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The polar-to-nonpolar interface of DyScO 3 and SrTiO 3 was studied using density functional theory. Due to the polar discontinuity arising from nominally charged DyO or ScO 2 layers, sharp interfaces induce a strong ferroelectriclike polarization in the SrTiO 3 , while in chemically mixed interfaces this discontinuity is avoided and no such polarization can be found. In both scenarios the interface remains insulating with only a small reduction of the band gap. Our calculations show that mixed interfaces are energetically more favorable than sharp ones, in agreement with recent experimental results that confirmed intermixing at these interfaces.

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Oxide superlattices with alternatingpandninterfaces

Cited by 72 publications

References 38 publications

Built-in and induced polarization across LaAlO3/SrTiO3 heterojunctions

Built-in and induced polarization across LaAlO3/SrTiO3 heterojunctions

First-principles study of intermixing and polarization at the DyScO3/SrTiO3interface

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