References of "Fontaine, Denis"
     in
Bookmark and Share    
Full Text
See detailOrigin and properties of the two-dimensional electron gas at the LaAlO3/SrTiO3 interface: a first-principles hybrid functional study.
Fontaine, Denis ULg

Doctoral thesis (2014)

Complex oxides exhibit a wide range of physical properties making them very attractive for future electronic and device applications. Although more and more studied, additional scientific investigations ... [more ▼]

Complex oxides exhibit a wide range of physical properties making them very attractive for future electronic and device applications. Although more and more studied, additional scientific investigations are required, especially in oxide interfaces, where new and amazing phenomena can arise. A prototypical example is the LaAlO3-SrTiO3 interface that appear to be conducting, magnetic or even supra-conducting while these properties are not present in the LaAlO3 and SrTiO3 bulk insulator compounds. The conductivity arises from the formation of a highly localized electron gas at the interface which exhibits a different behavior than the one at semiconductor interfaces. Even nowadays, its exact origin, intrinsic versus extrinsic, is still intensively debated. The existence of an electric field in LaAlO3 used as a key feature of models based on an intrinsic origin is highly controversial. In these models, the closing of the band gap with increasing LaAlO3 film thicknesses finally results to a Zener breakdown and to the metal/insulator transition. In this Ph.D. thesis we aim to investigate the various consequences of the presence of an electric field in LaAlO3 through first-principles calculations in pristine LaAlO3-SrTiO3 interfaces. First, using both experimental and theoretical structural distortions in LaAlO3, we predicted a lattice expansion via an electrostrictive effect, supporting the existence of an electric field in LaAlO3. Second, the metal/insulator transition was tuned with regards to the intensity of the electric field in the film, which was controlled by the composition of a solid solution between LaAlO3 and SrTiO3. The theoretical results match the experimental one where, nevertheless, extrinsic origin mechanisms are allowed and defects are present. These two works are in favors of an intrinsic origin of the electronic gas observed in LaAlO3-SrTiO3 heterostructures. In addition, a relationship between the sheet carrier density and spatial extension of the gas was established and thus setting an intrinsic threshold to the sheet carrier concentration. At lower density the electrons are strictly localized close to the interface while above this value the carriers start to spill into the SrTiO3 substrate. [less ▲]

Detailed reference viewed: 7 (3 ULg)
Full Text
Peer Reviewed
See detailDoping-dependent band structure of LaAlO3/SrTiO3 interfaces by soft x-ray polarization-controlled resonant angle-resolved photoemission
Cancellieri, C.; Reinle-Schmitt, M.L.; Kobayashi, M. et al

in Physical Review B (2014), 89

Polarization-controlled synchrotron radiation was used to map the electronic structure of buried conducting interfaces of LaAlO3/SrTiO3 in a resonant angle-resolved photoemission experiment. A strong ... [more ▼]

Polarization-controlled synchrotron radiation was used to map the electronic structure of buried conducting interfaces of LaAlO3/SrTiO3 in a resonant angle-resolved photoemission experiment. A strong polarization dependence of the Fermi surface and band dispersions is demonstrated, highlighting different Ti 3d orbitals involved in two-dimensional (2D) conduction. Measurements on samples with different doping levels reveal different band occupancies and Fermi-surface areas.The photoemission results are directly compared with advanced first-principles calculations, carried out for different 3d-band filling levels connected with the 2D mobile carrier concentrations obtained from transport measurements, with indication of charge localization at the interface. [less ▲]

Detailed reference viewed: 10 (3 ULg)
Full Text
Peer Reviewed
See detailTunable conductivity threshold at polar oxide interfaces
Reinle-Schmitt, M.L.; Cancellieri, C.; Li, D. et al

in Nature Communications (2012), 3

The physical mechanisms responsible for the formation of a two-dimensional electron gas at the interface between insulating SrTiO3 and LaAlO3 have remained a contentious subject since its discovery in ... [more ▼]

The physical mechanisms responsible for the formation of a two-dimensional electron gas at the interface between insulating SrTiO3 and LaAlO3 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 SrTiO3 and LaAlO3, and extrinsic mechanisms attributed to structural imperfections. Here we show that interface conductivity is also exhibited when the LaAlO3 layer is diluted with SrTiO3, and that the threshold thickness required to show conductivity scales inversely with the fraction of LaAlO3 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. [less ▲]

Detailed reference viewed: 46 (19 ULg)
Full Text
Peer Reviewed
See detailSpontaneous 2-Dimensional Carrier Confinement at the n-Type SrTiO3=LaAlO3 Interface
Delugas, P.; Filippetti, A.; Fiorentini, V. et al

in Physical Review Letters (2011), 106

We describe the intrinsic mechanism of 2-dimensional electron confinement at the n-type SrTiO3=LaAlO3 interface as a function of the sheet carrier density ns via advanced first-principles calculations ... [more ▼]

We describe the intrinsic mechanism of 2-dimensional electron confinement at the n-type SrTiO3=LaAlO3 interface as a function of the sheet carrier density ns via advanced first-principles calculations. Electrons localize spontaneously in Ti 3dxy levels within a thin (& 2 nm) interface-adjacent SrTiO3 region for ns lower than a threshold value nc 1014 cm 2. For ns >nc a portion of charge flows into Ti 3dxz-dyz levels extending farther from the interface. This intrinsic confinement can be attributed to the interface-induced symmetry breaking and localized nature of Ti 3d t2g states. The sheet carrier density directly controls the binding energy and the spatial extension of the conductive region. A direct, quantitative relation of these quantities with ns is provided. [less ▲]

Detailed reference viewed: 16 (6 ULg)
Full Text
Peer Reviewed
See detailElectrostriction at the LaAlO3/SrTiO3 Interface
Cancellieri, C.; Fontaine, Denis ULg; Gariglio, S. et al

in Physical Review Letters (2011), 107

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 ... [more ▼]

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. [less ▲]

Detailed reference viewed: 17 (5 ULg)
See detailTheory and modelling of functional materials. Running activities at ULg
Fontaine, Denis ULg

Scientific conference (2010, June)

Detailed reference viewed: 17 (7 ULg)