Instability, intermixing and electronic structure at the epitaxial <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" altimg="si51.gif" display="inline" overflow="scroll"><mml:msub><mml:mrow><mml:mstyle mathvariant="normal"><mml:mi>LaAlO</mml:mi></mml:mstyle></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub><mml:mo>/</mml:mo><mml:msub><mml:mrow><mml:mstyle mathvariant="normal"><mml:mi>SrTiO</mml:mi></mml:mstyle></mml:mrow><mml:mrow><mml:mn>3</mml:mn></mml:mrow></mml:msub><mml:mrow><mml:mo>

Chambers, Scott A.; Engelhard, Mark H.; Shutthanandan, V.; Zhu, Zihua; Droubay, Timothy C.; Qiao, Liang; Sushko, Peter V.; Feng, Tingting; Lee, H. D.; Gustafsson, T.; Garfunkel, Eric; Shah, Amish B.; Zuo, Jian‐Min; Ramasse, Quentin M.

doi:10.1016/j.surfrep.2010.09.001

Cited by 287 publications

(249 citation statements)

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“…Since its discovery 2 several competing mechanisms have been proposed and intensely debated to explain the origin of the interfacial 2D electron gas, including electronic reconstruction, 19 oxygen vacancies in the SrTiO 3 substrate, [20][21][22] and intermixing between the LaAlO 3 film and the SrTiO 3 substrate. 23,24 According to the electronic reconstruction mechanism, because the atomic layers are charge neutral in SrTiO 3 but charged in LaAlO 3 , a diverging electric potential is built up in a LaAlO 3 film grown on a TiO 2 -terminated SrTiO 3 substrate. This leads to the transfer of half of an electron from the LaAlO 3 film surface to SrTiO 3 when the LaAlO 3 layer is thicker than 4 unit cells, creating a 2D electron gas at the interface with a sheet carrier density of 3.3 × 10 14 /cm 2 for sufficiently thick LaAlO 3 .…”

Section: Resultsmentioning

confidence: 99%

Constructing oxide interfaces and heterostructures by atomic layer-by-layer laser molecular beam epitaxy

et al. 2017

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Advancements in nanoscale engineering of oxide interfaces and heterostructures have led to discoveries of emergent phenomena and new artificial materials. Combining the strengths of reactive molecular-beam epitaxy and pulsed-laser deposition, we show here, with examples of Sr 1+x Ti 1-x O 3+δ , Ruddlesden-Popper phase La n+1 Ni n O 3n+1 (n = 4), and LaAl 1+y O 3(1+0.5y) /SrTiO 3 interfaces, that atomic layer-by-layer laser molecular-beam epitaxy significantly advances the state of the art in constructing oxide materials with atomic layer precision and control over stoichiometry. With atomic layer-by-layer laser molecular-beam epitaxy we have produced conducting LaAlO 3 /SrTiO 3 interfaces at high oxygen pressures that show no evidence of oxygen vacancies, a capability not accessible by existing techniques. The carrier density of the interfacial two-dimensional electron gas thus obtained agrees quantitatively with the electronic reconstruction mechanism.npj Quantum Materials (2017) 2:10 ; doi:10.1038/s41535-017-0015-x INTRODUCTION Technological advances in atomic-layer control during oxide film growth have enabled the discoveries of new phenomena and new functional materials, such as the two-dimensional (2D) electron gas at the LaAlO 3 /SrTiO 3 interface, 1, 2 and asymmetric three-component ferroelectric superlattices. 3,4 Reactive molecular-beam epitaxy (MBE) and pulsed-laser deposition (PLD) are the two most successful growth techniques for epitaxial heterostructures of complex oxides. PLD possesses experimental simplicity, low cost, and versatility in the materials to be deposited. 5 Reactive MBE employing alternately-shuttered elemental sources (atomic layerby-layer MBE, or ALL-MBE) can control the cation stoichiometry precisely, thus producing oxide thin films of exceptional quality. [6][7][8] There are, however, limitations in both techniques. Reactive MBE can use only source elements whose vapor pressure is sufficiently high, excluding a large fraction of 4d and 5d metals. In addition, ozone is needed to create a highly oxidizing environment while maintaining low-pressure MBE conditions, which increases the system complexity. On the other hand, conventional PLD using a compound target often results in cation off-stoichiometry in the films. 9, 10 In this paper we present an approach that combines the strengths of reactive MBE and PLD: atomic layer-by-layer laser MBE (ALL-Laser MBE) using separate oxide targets. Ablating alternately the targets of constituent oxides, for example SrO and TiO 2 , a SrTiO 3 film can be grown one atomic layer at a time. Stoichiometry for both the cations and oxygen in the oxide films can be controlled. Although the idea of depositing atomic layers by PLD has been explored since the early days of laser MBE, 11,12 we show that levels of stoichiometry control and crystalline perfection rivaling those of

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Section: Resultsmentioning

confidence: 99%

Constructing oxide interfaces and heterostructures by atomic layer-by-layer laser molecular beam epitaxy

et al. 2017

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“…However, structural and XAS spectroscopic data [37], core-level photoemission spectroscopy [50], second har-monic generation [83] suggest an orbital reconstruction below the critical thickness.…”

Section: Discussion and Concluding Remarksmentioning

confidence: 98%

Electronic Reconstruction at the Interface Between Band Insulating Oxides: The LaAlO3/SrTiO3 System

Salluzzo

2015

Oxide Thin Films, Multilayers, and Nanocomposites

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The conducting quasi-two dimensional electron system (q2DES) formed at the interface between LaAlO 3 and SrTiO 3 band insulators is confronting the condensed matter physics community with new paradigms. While the mechanism for the formation of the q2DES is debated, new conducting interfaces have been discovered paving the way to possible applications in electronics, spintronics and optoelectronics. This chapter is an overview of the research on the LAO/STO system, presenting some of the most important results obtained in the last decade to clarify the mechanism of formation of the q2DES at the oxide interfaces and its peculiar electronic properties as compared to semiconducting 2D-electron gas.

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“…There have been other proposed mechanisms for the origin of carriers at the interface, which are based on defects in STO bulk, cation intermixing, and oxygen vacancies near the interface. [25][26][27] These issues will be not be dealt with in this paper.…”

Section: Introductionmentioning

confidence: 99%

First-principles study of surface charging inLaAlO3/SrTiO3heterostructures

et al. 2015

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The two-dimensional electron gas (2DEG) observed at the interface between LaAlO3 (LAO) and SrTiO3 (STO) is known to be very sensitive to the proximity of the LaAlO3 surface and the conditions to which the surface is exposed. We use first-principles calculations to study surface reconstructions on LAO films, taking into account that the LAO surface can be charged. The results for the charged surfaces and for the coupling between the surface and the 2DEG enable us to account not only for the behavior of the 2DEG as a function of thickness of the LAO layer, but simultaneously determine the stable terminations and reconstructions on the LAO surface under a variety of conditions. Our studies of charged surfaces are based on an extension of the methodology of Lozovoi et al. [J. Chem. Phys. 115, 1661(2001]. From the calculated electronic structure of the unreconstructed (but relaxed) AlO2 and LaO surface terminations of LAO, we find surface states having excess holes (AlO2 termination) or excess electrons (LaO termination). This result is central to understanding the mechanism of 2DEG formation, and is consistent with a 2DEG of density 3.3×10 14 cm −2 being intrinsic to the LaO-TiO2 interface in the LAO/STO system. We explore the effects of the Al-adatom, O-vacancy and H-adatom surface reconstructions on the 2DEG density, and find that the stability of different reconstructions is tied to the thickness of the LAO layer as well as the surface exposure conditions. We find that including the effects of charging of the surface significantly stabilizes the AlO2 termination versus the LaO termination. Overall, our methodology has the advantage of decoupling first-principles calculations for the interface from those for the charged surface, and constitutes a general approach that can be applied to the commonly occurring problem of charge exchange between the surface and the interface of a thin film with a substrate, or between the surface and defects/impurities in the bulk of a material.

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Instability, intermixing and electronic structure at the epitaxial LaAlO3/SrTiO3

Cited by 287 publications

References 100 publications

Constructing oxide interfaces and heterostructures by atomic layer-by-layer laser molecular beam epitaxy

Constructing oxide interfaces and heterostructures by atomic layer-by-layer laser molecular beam epitaxy

Electronic Reconstruction at the Interface Between Band Insulating Oxides: The LaAlO3/SrTiO3 System

First-principles study of surface charging inLaAlO3/SrTiO3heterostructures

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