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Univ. Paris-Saclay

Sujet de stage / Master 2 Internship

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Multifunctionnal multiferroic oxynitride thin films for opto-electronics

Contact: BARBIER Antoine, , antoine.barbier@cea.fr, +33 1 69 08 39 23
Summary:
The objective of the internship is to grow epitaxial thin multiferroic ferrite/perovskite (CoFe2(OxN1-x)4/BaTi(OxN1-x)3 oxinitride films by oxygen and nitrogen plasma assisted molecular beam epitaxy: a potentially visible light sensitive ferroelectric and ferrimagnetic material. We will proceed by nitrogen doping of CoFe2O4/BaTiO3 for which the growth conditions are already mastered in the CEA/SPEC laboratory. Potential application to opto-spintronics will be studied in the laboratory, at C2N and at synchrotron-SOLEIL.
Possibility of continuation in PhD: Oui
Deadline for application:30/04/2021

Full description:
Novel materials are required within the energy transition framework, in particular to produce clean energy and/or reduce electronic device consumption and overall materials usage. Within this context oxynitrides are a relevant class of materials. The ferroelectric ones are very well suited to realize opto-spintronic sensors. 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 laminar oxide multiferroic films of cobalt ferrite (CoFe2O4, ferromagnetic) deposited on barium titanate (BaTiO3, ferroelectric). Its growth conditions are already well mastered and we will proceed by the addition of nitrogen plasma during growth. We will study the influence of the N doping on the magnetic properties at CEA/SPEC and on the ferroelectric ones at C2N after lithography. Ideally, the ratio between the loss of ferroelectricity / ferrimagnetism and the gain of photosensitivity will be quantified. X-ray measurements may be used to characterize the material developed on the DiffAbs, HERMES, DEIMOS and/or CASSIOPEE beamlines at the SOLEIL synchrotron.

The student will be supervised by S. Matzen during his/her work at C2N and by R. Belkhou (HERMES beamline) during his/her work at synchrotron SOLEIL.

Contacts : BARBIER Antoine, +33 1 69 08 39 23, antoine.barbier@cea.fr ; Other researchers : H. Magnan, S. Matzen (C2N), J.-B. Moussy and C. Mocuta (Synchrotron-SOLEIL). Synchrotron-SOLEIL beamlines associated with the project : HERMES (R. Belkhou), DEIMOS (P. Ohresser), CASSIOPEE (P. LeFevre)
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), magnetic measurements (VSM), lithography and ferroelectric measurements at (C2N) and X-ray diffraction.

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