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Séminaire général de l’INSP

Interface effects at all-oxide epitaxial heterojunctions – Luigi Sangaletti – Jeudi 21 septembre 2017 à 11 h

INSP - UPMC - 4 place Jussieu - 75005 Paris - Barre 22-23, 3e étage, salle 317

Luigi Sangaletti - Interdisciplinary Laboratories for Advanced Materials Physics (I-LAMP) - Università Cattolica de Brescia (Italy)

Abstact

Recent advances in the growth of epitaxial oxide thin films have fostered a steady increase of research on perovskite oxide heterojunctions, which are now produced with unprecedented quality. Applications of these ultra-thin interfaces in the field of electronics, photon harvesting, photovoltaics and photocatalysis strongly rely on the capability to master band gap engineering at the nanoscale. X-ray photoemission spectroscopies (XPS) are playing a key role in the investigation of electronic and structural properties of all-oxide heterointerfaces [1]. Core level and valence band XPS can be combined to probe the band gap alignment [2]. The use of tunable light sources allow to change the in-depth sensitivity, with the possibility to profile the band-gap close to the interface and compare the results with bulk electronic states [3]. Furthermore, angle-resolved XPS spectra can probe the local order around the photoemitting atom, but through suitable modeling these data can also be used to track cation interdiffusion across the interfaces [4]. Finally, the spectral weight enhancement obtained by tuning the photon energy [5], has disclosed unexpected possibilities in the study of band dispersion at buried interfaces. Here, the combination of these techniques is focused on perovskite oxide layers (in particular LaAlO3) grown on SrTiO3, as these systems can host a two dimensional electron gas (2DEG) at the interface and display magnetic ordering and superconductivity effects, disclosing possible applications in the next-generation nanoelectronic devices. Electron spectroscopy results add important details to the physics of these systems, displaying a far richer scenario with respect to the bare electronic reconstruction. In particular, origin and signatures of the 2DEG are discussed in connection with cation interdiffusion and surface cation substoichiometry.

[1] A Giampietri, G Drera, L Sangaletti, Advanced Materials Interfaces, 4(2017) 1700144
[2] G Drera, G Salvinelli, A Brinkman, et al. PRB B 87 (2013) 075435
[3] G Drera, G Salvinelli, F Bondino, et al., PRB B 90 (2014) 035124
[4] G Salvinelli, G Drera, A Giampietri, L Sangaletti ACS-AMI 7 (2015), 25648