Locally enhanced conductivity due to the tetragonal domain structure in LaAlO3/SrTiO3 heterointerfaces

Kalisky, Beena; Spanton, Eric; Noad, Hilary; Kirtley, J. R.; Nowack, Katja C.; Bell, C. H.; Sato, Hiroki; Hosoda, Masayuki; Xie, Yanwu; Hikita, Y.; Woltmann, Carsten; Pfanzelt, Georg; Jany, R.; Richter, Christoph; Hwang, Harold Y.; Mannhart, J.; Moler, Kathryn A.

doi:10.1038/nmat3753

Cited by 203 publications

(262 citation statements)

References 41 publications

(47 reference statements)

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“…72 In addition, in the recent past, a great deal of research activity has centred around the findings of an unexpected phenomenon such as two-dimensional electron gas (2DEG), ferromagnetism and superconductivity, which have been discovered to exist at the interface between STO and other nonmagnetic insulating oxides. [73][74][75] A pristine STO single crystal is an ideal DM material due to the absence of unpaired electrons. Doping of (Mn 76 and Nb 77 ) STO crystal and thin films has been shown to be one means of inducing ferromagnetism.…”

Section: Srtio 3 Single Crystalsmentioning

confidence: 99%

Multifunctional heterostructures integrated on Si (100)

Singamaneni

Prater

Narayan

2015

Emerging Materials Research

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This paper focuses on the growth of several important oxide systems, including BiFeO 3 (BFO), La 0·7 Sr 0·3 MnO 3 (LSMO), BaTiO 3 (BTO), and non-oxide films including permalloy/MgO and Ni/MgO. It is shown that one can achieve thin-film epitaxy over an extended misfit scale by using the paradigm of DME. This will be critical for the future integration of multifunctional heterostructures onto CMOS-based chips in order to create smart structures for the next-generation solid-state devices. In addition, this paper explores the utility of using laser processing to introduce defect populations that induce magnetism in non-magnetic oxides such as STO and BTO as an alternative to incorporating more traditional magnetic layers into the structure. IntroductionThe integration of complex oxide films and heterostructures within existing electronics can significantly expand the range of functional properties available for device exploitation, including colossal magneto-resistance, magnetocaloric effects, coupled magnetic and polarisation (multiferroic) behaviour, and some interesting physical phenomena including spin, charge and orbital ordering. As a result, there has been a tremendous increase in research related to the deposition of multifunctional thin-film heterostructures for solid-state device technology.1-3 The realization of these expected capabilities requires the integration of various multifunctional materials on substrates of industrial interest, particularly integration with existing silicon (Si)-integrated circuits where total misfit strain can range from 1% up to as much as 25%.4,5 Thus, strain and defect control in these films are essential. The total strain that develops in multilayer thin-film heterostructures has three primary components: (a) lattice misfit arising from the differences in lattice constants between the film and the substrate, (b) thermal misfit arising from differences in coefficients of thermal expansion and (c) microstructural strains arising from defects and alloying elements (dopants). By far the largest of these components is the misfit strain. This paper primarily addresses minimization of the lattice misfit component of the strain.According to conventional wisdom, as outlined under the latticematching epitaxy (LME) paradigm, thin films grow as epitaxial Multifunctional heterostructures integrated on Si (100) Singamaneni, Prater and Narayan ICE Publishing: All rights reserved

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Section: Srtio 3 Single Crystalsmentioning

confidence: 99%

Multifunctional heterostructures integrated on Si (100)

Singamaneni

Prater

Narayan

2015

Emerging Materials Research

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“…Tunneling [16,17] and SQUID magnetometry [18] provide clear evidence of an inhomogeneous interface on both micro-and nanoscopic scales. Transport measurements report further signs of inhomogeneity and a percolative metal-to-superconductor transition with a sizable fraction of the 2DEG never becoming superconducting down to the lowest accessible temperatures [19][20][21][22].…”

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confidence: 99%

Phase Separation from Electron Confinement at Oxide Interfaces

et al. 2016

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Oxide heterostructures are of great interest both for fundamental and applicative reasons. In particular the two-dimensional electron gas at the LaAlO3/SrTiO3 or LaTiO3/SrTiO3 interfaces displays many different physical properties and functionalities. However there are clear indications that the interface electronic state is strongly inhomogeneous and therefore it is crucially relevant to investigate possible intrinsic electronic mechanisms underlying this inhomogeneity. Here the electrostatic potential confining the electron gas at the interface is calculated self-consistently, finding that the electron confinement at the interface may induce phase separation, to avoid a thermodynamically unstable state with a negative compressibility. This provides a generic robust and intrinsic mechanism for the experimentally observed inhomogeneous character of these interfaces.PACS numbers: 73.43.Nq,73.21.Fg, The two-dimensional electron gas (2DEG) that forms at the interface of two insulating oxides, like LaAlO 3 /SrTiO 3 and LaTiO 3 /SrTiO 3 (hereafter generically referred to as LXO/STO) [1][2][3][4], exhibits a rich phenomenology, such as a gate-tunable metal-tosuperconductor transition [5][6][7][8], a magnetic-field-tuned quantum criticality [9], and inhomogeneous magnetic responses [10][11][12][13][14][15]. Tunneling [16,17] and SQUID magnetometry [18] provide clear evidence of an inhomogeneous interface on both micro-and nanoscopic scales. Transport measurements report further signs of inhomogeneity and a percolative metal-to-superconductor transition with a sizable fraction of the 2DEG never becoming superconducting down to the lowest accessible temperatures [19][20][21][22]. For both fundamental reasons and applicative purposes, like device design, it is crucial to identify possible intrinsic mechanisms that may render the 2DEG so strongly inhomogeneous via a phase separation (PS). This is precisely the focus of the present work.Here, we identify a very effective electron-driven mechanism leading to PS, based on the confinement of the 2DEG at the interface. From customary self-consistent calculations of the confining potential well in semiconductors, it is well known [23] that a finite lateral extension usually renders the 2DEG more compressible than its strictly 2D counterpart. This effect is much stronger in LXO/STO than in ordinary semiconductor interfaces, due to the huge dielectric constant of STO, allowing for much larger electron densities, with a strong amplification of the self-consistent adjustments of the confining potential. As a consequence, a non-rigid band structure arises, which varies with the local electron density: an increased electron density is accompanied by a corresponding increase of the positive countercharges (due to oxygen vacancies and/or polarity catastrophe [24][25][26][27][28][29]), from which the interfacial electrons are introduced and restoring the overall charge neutrality. For small-to-moderate increases of electron and countercharge densities the potential well deepens and the e...

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“…17 More recently, the presence of tetragonal domains in STO (at low temperature) was demonstrated to alter locally the conductance. 18,19 Finally, the control of the LAO surface state was shown to be an efficient lever to enhance the interfacial electron mobility. 8,20,21 In this letter, we perform a systematic study of the effect of the growth temperature (T g ) on the transport properties of the LAO/STO interface.…”

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confidence: 99%

Growth-induced electron mobility enhancement at the LaAlO3/SrTiO3 interface

Fête

Cancellieri

et al. 2015

Applied Physics Letters

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We have studied the electronic properties of the 2D electron liquid present at the LaAlO3/SrTiO3 interface in series of samples prepared at different growth temperatures. We observe that interfaces fabricated at 650 °C exhibit the highest low temperature mobility (≈10 000 cm2 V−1 s−1) and the lowest sheet carrier density (≈5×1012 cm−2). These samples show metallic behavior and Shubnikov-de Haas oscillations in their magnetoresistance. Samples grown at higher temperatures (800–900 °C) display carrier densities in the range of ≈2−5×1013 cm−2 and mobilities of ≈1000 cm2 V−1 s−1 at 4 K. Reducing their carrier density by field effect to 8×1012 cm−2 lowers their mobilities to ≈50 cm2 V−1 s−1 bringing the conductance to the weak-localization regime.

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Locally enhanced conductivity due to the tetragonal domain structure in LaAlO3/SrTiO3 heterointerfaces

Cited by 203 publications

References 41 publications

Multifunctional heterostructures integrated on Si (100)

Multifunctional heterostructures integrated on Si (100)

Phase Separation from Electron Confinement at Oxide Interfaces

Growth-induced electron mobility enhancement at the LaAlO3/SrTiO3 interface

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