Thesis

N-doped oxides and/or oxinitrides constitute a booming class of compounds with a broad spectrum of useable properties and in particular for novel technologies of carbon-free energy production. Indeed, the insertion of nitrogen into the crystal lattice of a semiconductor oxide allows, in principle, to modulate the value of its band gap or to introduce additional electronic states and thus to obtain new functionalities and optical properties. The production of oxynitride single crystalline thin films is highly challenging. In this essentially experimental thesis work, thin films of oxynitrides will be developed by atomic plasma-assisted molecular beam epitaxy. We will start from BaTiO3, which synthesis is well mastered in the laboratory, to realize co-dopings with nitrogen and compensating metals in order to preserve the neutrality of the elementary unit cell. The resulting structures will be studied for their chemical compositions, crystalline structures and ferroelectric characteristics. These observations will be correlated with their performance for the photo-electrolysis of water, which allows the virtuous production of hydrogen. Finally, the corrosion resistance of these new materials will also be studied.
The student will acquire skills in a wide range of ultra-high vacuum techniques, molecular beam epitaxy growth, clean room lithography, ferroelectric measurements and photo-electrolysis of water, as well as in state-of-the-art synchrotron radiation techniques.