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ABSTRACT: The interfaces of LaAlO_{3}/SrTiO_{3} and (LaAlO_{3})_{x}(SrTiO_{3})_{1-x}/SrTiO_{3} heterostructures have been investigated by soft x-ray photoelectron spectroscopy for different layer thicknesses across the insulator-to-metal interface transition. The valence band and Fermi edge were probed using resonant photoemission across the Ti L_{2,3} absorption edge. The presence of a Fermi-edge signal originating from the partially filled Ti 3d orbitals is only found in the conducting samples. No Fermi-edge signal could be detected for insulating samples below the critical thickness. Furthermore, the angular dependence of the Fermi intensity allows the determination of the spatial extent of the conducting electron density perpendicular to the interface.
Physical Review Letters 03/2013; 110(13):137601. · 7.37 Impact Factor
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M L Reinle-Schmitt, C Cancellieri,
D Li,
D Fontaine,
M Medarde,
E Pomjakushina,
C W Schneider,
S Gariglio,
Ph Ghosez,
J-M Triscone,
P R Willmott
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ABSTRACT: The physical mechanisms responsible for the formation of a two-dimensional electron gas at the interface between insulating SrTiO(3) and LaAlO(3) have remained a contentious subject since its discovery in 2004. Opinion is divided between an intrinsic mechanism involving the build-up of an internal electric potential due to the polar discontinuity at the interface between SrTiO(3) and LaAlO(3), and extrinsic mechanisms attributed to structural imperfections. Here we show that interface conductivity is also exhibited when the LaAlO(3) layer is diluted with SrTiO(3), and that the threshold thickness required to show conductivity scales inversely with the fraction of LaAlO(3) in this solid solution, and thereby also with the layer's formal polarization. These results can be best described in terms of the intrinsic polar-catastrophe model, hence providing the most compelling evidence, to date, in favour of this mechanism.
Nature Communications 01/2012; 3:932. · 7.40 Impact Factor
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M. L. Reinle-Schmitt, C Cancellieri,
D. Li,
D. Fontaine,
M. Medarde,
E. Pomjakushina,
C. W. Schneider,
S. Gariglio,
Ph. Ghosez,
J-M Triscone,
P. R. Willmott
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ABSTRACT: The predictions of the polar catastrophe scenario to explain the occurrence
of a metallic interface in heterostructures of the solid
solution(LaAlO$_3$)$_{x}$(SrTiO$_3$)$_{1-x}$ (LASTO:x) grown on (001) SrTiO$_3$
were investigated as a function of film thickness and $x$. The films are
insulating for the thinnest layers, but above a critical thickness, $t_c$, the
interface exhibits a constant finite conductivity which depends in a
predictable manner on $x$. It is shown that $t_c$ scales with the strength of
the built-in electric field of the polar material, and is immediately
understandable in terms of an electronic reconstruction at the nonpolar-polar
interface. These results thus conclusively identify the polar-catastrophe model
as the intrinsic origin of the doping at this polar oxide interface.
12/2011;
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C Cancellieri,
D Fontaine,
S Gariglio,
N Reyren,
A D Caviglia,
A Fête,
S J Leake,
S A Pauli,
P R Willmott,
M Stengel,
Ph Ghosez,
J-M Triscone
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ABSTRACT: We present a direct comparison between experimental data and ab initio calculations for the electrostrictive effect in the polar LaAlO(3) layer grown on SrTiO(3) substrates. From the structural data, a complete screening of the LaAlO(3) dipole field is observed for film thicknesses between 6 and 20 uc. For thinner films, an expansion of the c axis of 2% matching the theoretical predictions for an electrostrictive effect is observed experimentally.
Physical Review Letters 07/2011; 107(5):056102. · 7.37 Impact Factor
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C. Cancellieri,
D. Fontaine,
S. Gariglio,
N. Reyren,
A. D. Caviglia,
A. Fête,
S. J. Leake,
S. A. Pauli,
P. R. Willmott,
M. Stengel,
Ph. Ghosez,
J.-M. Triscone
[show abstract]
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ABSTRACT: We present a direct comparison between experimental data and ab initio calculations for the electrostrictive effect in the polar LaAlO3 layer grown on SrTiO3 substrates. From the structural data, a complete screening of the LaAlO3 dipole field is observed for film thicknesses between 6 and 20 uc. For thinner films, an expansion of the c axis of 2% matching the theoretical predictions for an electrostrictive effect is observed experimentally.
Physical Review Letters 07/2011; 107(5):056102. · 7.37 Impact Factor
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ABSTRACT: We report on a study of magnetotransport in LaAlO3 /SrTiO3 interfaces characterized by mobilities of the order of several thousands cm2/V s. We observe Shubnikov-de Haas oscillations whose period depends only on the perpendicular component of the magnetic field. This observation directly indicates the formation of a two-dimensional electron gas originating from quantum confinement at the interface. From the temperature dependence of the oscillation amplitude we extract an effective carrier mass m* ≃ 1.45 m(e). An electric field applied in the back-gate geometry increases the mobility, the carrier density, and the oscillation frequency.
Physical Review Letters 12/2010; 105(23):236802. · 7.37 Impact Factor
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ABSTRACT: The effects of oxygen pressure during the growth of LaAlO3 on (001) SrTiO3, and of post-deposition annealing were investigated. While little influence on the structure was observed, the transport properties were found to depend on both growth pressure and annealing. For LaAlO3 layer thicknesses between 5 and 10 unit cells and growth pressures between 10− 4 and 10−2 mbar, the LaAlO3/SrTiO3 interfaces displayed similar metallic behavior with a sharp transition to a superconducting state. At an oxygen pressure of 10− 6 mbar oxygen vacancies were clearly introduced and extended deep into the SrTiO3 crystal. These vacancies could be removed by post-deposition annealing in 0.2 bar of O2 at ~530 °C. At a growth pressure of 10− 4 mbar, the electronic properties of samples with ultra-thin LaAlO3 layers (2 to 3 unit cells thick) were found to depend markedly on the post-annealing step.
EPL (Europhysics Letters) 07/2010; 91(1):17004. · 2.17 Impact Factor
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ABSTRACT: The quasi-two-dimensional electron gas found at the LaAlO{3}/SrTiO{3} interface offers exciting new functionalities, such as tunable superconductivity, and has been proposed as a new nanoelectronics fabrication platform. Here we lay out a new example of an electronic property arising from the interfacial breaking of inversion symmetry, namely, a large Rashba spin-orbit interaction, whose magnitude can be modulated by the application of an external electric field. By means of magnetotransport experiments we explore the evolution of the spin-orbit coupling across the phase diagram of the system. We uncover a steep rise in Rashba interaction occurring around the doping level where a quantum critical point separates the insulating and superconducting ground states of the system.
Physical Review Letters 03/2010; 104(12):126803. · 7.37 Impact Factor
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http://dx.doi.org/10.1209/0295-5075/91/17004.
