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Communication Dans Un Congrès Année : 2022

X-ray spectroscopy analysis of the chemical and electronic structure of BaTiO3 ultrathin films

Sara Gonzalez
Patrick Schöffmann
  • Fonction : Auteur
  • PersonId : 1155955
Edwige Otero
  • Fonction : Auteur
  • PersonId : 1155956
Nicolas Baboux
Brice Gautier
Philippe Ohresser
Ingrid C. Infante

Résumé

Nano ferroelectricity has promising technological applications as energy-saving, low-sized electronic devices. Tunnel junctions and transistors using ferroelectric gates are examples of potential applications [1]. BaTiO3 (BTO) is a lead-free ferroelectric showing fascinating properties when connected to an electrode, in particular a “positive dead-layer” [2] or interface ionic relaxation [3], making BTO a promising candidate for integration in multifunctional structures with ultimate nanoscale dimensions. For this purpose, the physical and chemical properties of interfaces and ultrathin layers based on BTO have to be understood and means to control their properties must be sought out. In this work, we propose to study ultrathin BTO films grown by industrially scalable magnetron sputtering on conductive Nb-doped SrTiO3 substrates and on structurally compatible conductive layers of SrRuO3, with capping electrodes defining BTO-capacitors, to explore the effect of the conduction and chemical reconstruction phenomena within the films and at the different interfaces. The average structure and strain of BTO films from 2 to 16 nm were investigated using X-ray diffraction. A thorough spectroscopic analysis of the films was carried out to study the relationship between strain and materials and processing parameters. Combining synchrotron X-ray absorption spectroscopy in capacitors and laboratory X-ray photoelectron spectroscopy, we probed the electronic structure under the influence of different UHV annealing conditions, studied the promotion of electronic and ionic defects, e.g. oxygen vacancies. Structural and polarization states of differently strained BTO films were analyzed through X-ray natural linear dichroism at the Ti-L2,3 edges along with multiplet calculations supporting the experimental evidence of the contribution of the strain to the polarization of the films. Scanning transmission electron microscopy and electron energy loss electron spectroscopy provided the atomic scale evidences of the electronic structure through the films and at the interfaces. Combined with piezoresponse force microscopy and electrical characterizations to probe ferroelectric and electrical properties under electric field, these results are crucial to understand and master the underlying physical mechanisms leading to the ferroelectric properties of operating BTO-based devices. This work is supported by collaborative VOLCONANO ANR-19-CE09-0023 project. [1] Scott, J.F. Science 315, 954 -959 (2007) [2] Stengel, M., Vanderbilt, D. & Spaldin, N.A. Nature Materials 8, 392-397 (2009). [3] Gerra G., Tagantsev A. K., and Setter N., Physical Review Letters 98, 207601 (2007).
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Dates et versions

hal-03750617 , version 1 (23-08-2022)

Identifiants

  • HAL Id : hal-03750617 , version 1

Citer

Sara Gonzalez, Pedro Rojo Romeo, Matthieu Bugnet, Patrick Schöffmann, Edwige Otero, et al.. X-ray spectroscopy analysis of the chemical and electronic structure of BaTiO3 ultrathin films. ISAF-PFM-ECAPD 2022, IEEE UFFC, Jun 2022, Tours, France. ⟨hal-03750617⟩
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