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Univ. Paris-Saclay

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N doped BaTiO3 multifunctionnal thin films for opto-electronics and energy transition

Contact: BARBIER Antoine, , antoine.barbier@cea.fr, +33 1 69 08 39 23
Summary:
The objective of the internship is to grown thin BaTi(OxN1-x)3 oxinitride films by oxygen and nitrogen plasma assisted molecular beam epitaxy: a visible light sensitive ferroelectric material. We will proceed by nitrogen doping of BaTiO3 for which the growth conditions are perfectly mastered in the CEA/SPEC laboratory. Potential application to water-splitting and/or opto-spintronics will be studied in the laboratory and potentially at C2N and at synchrotron-SOLEIL.
Possibility of continuation in PhD: Oui
Deadline for application:30/04/2020

Full description:
Novel materials are required within the energy transition framework, in particular to produce clean energy and/or reduce electronic device consumption. Within this context oxynitrides are a relevant class of materials. The ferroelectric ones are very well suited to realize opto-spintronic sensors or electrode materials for hydrogen production through solar water splitting. The insertion of nitrogen, less electronegative than oxygen, into the lattice of an oxide causes an increase in the covalent nature of the chemical bonds. This leads to a decrease of the optical gap, Eg, value and thus in a modification of the absorption properties of the compound as well as doping by charge carriers making it possible to envisage new transport properties. The production of single crystalline thin oxynitride films is however challenging and has been little studied to date.
We will explore the possibility of modulating the properties of thin films of barium titanate, BaTiO3, a ferroelectric oxide. Its growth conditions are already well mastered and we will proceed by the addition of nitrogen plasma during growth. Ideally, the ratio between the loss of ferroelectricity and the gain of activity as a photoanode in the photoelectrolysis of water will be quantified. The influence of visible light on the structures will be studied. If possible we will deposit a magnetic layer and study the influence of the N doping on the magnetic properties. X-ray diffraction measurements may be used to characterize the material developed on the DiffAbs beamline at the SOLEIL synchrotron as well as ferroelectric measurements on patterned samples at C2N.

Contacts: BARBIER Antoine, +33 1 69 08 39 23, antoine.barbier@cea.fr
Additional implicated researchers: H. Magnan, S. Matzen (C2N), J.-B. Moussy and C. Mocuta (Synchrotron-SOLEIL) - The internship relies on a CEA, C2N, SOLEIL collaboration.
Technics/methods used during the internship:
The candidate will address the UHV techniques associated with the growth by molecular beam epitaxy. The techniques that will be used are Reflexion High Energy Electron Diffraction (RHEED), Auger Electron Spectroscopy (AES), Photoemission core level spectroscopy (XPS), Piezo Force Microscopy (PFM), Low Energy Electron microscopy (LEEM), a photoelectrocatalytic water-splitting setup, and eventually magnetic measurements (VSM), lithography (at C2N) and X-ray diffraction.

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