Description du sujet de thèse

Silicon photonics, i.e. the use of silicon for integrated photonic circuits, emerged on an industrial scale over a decade ago and is now a well-established technology. For future communication networks, new challenges need to be met in terms of speed, power consumption and flexibility. At C2N, we are exploring a new paradigm for advanced photonic circuits, based on the integration of crystalline oxides into the silicon photonics platform for telecommunication wavelengths (1.3µm-1.55µm). These oxides offer physical properties not found in silicon, such as ferroelectricity, making them highly attractive for advanced nonlinear and optoelectronic devices.
The thesis work will focus on the growth of doped zirconia (ZrO2) thin films on single-crystal substrates, and in particular on the study of the interaction between the dopant and substrate-induced deformation to stabilize a ZrO2 ferroelectric phase at a thickness of 50 nm or more. Stimulating results have already been obtained in this respect at C2N with ZrO2 films deposited by pulsed laser ablation (PLD), paving the way for the study of dopant engineering. A molecular beam epitaxy (MBE) system, installed in 2024 and dedicated to oxide thin films, will enable better control of the stoichiometry of these dopants and of the oxygen in these compounds. In particular, a multilayer and superlattice approach will be explored, to take advantage of the atomic-scale interface control enabled by MBE, while taking into account the stability of ZrO2 crystalline phases. BaTiO3 thin films will also be developed, to serve as a reference due to their well-established electro-optical properties and perfect control of their stoichiometry with organometallic precursor for MBE, as implemented at C2N.

Contexte de travail

C2N (Centre de Nanosciences et de Nanotechnologies) is a joint research unit of Université Paris-Saclay and CNRS. The laboratory employs around 410 people, including 80 engineers and technicians and 120 researchers. It is organized into 4 departments (Photonics, Nanoelectronics, Microsystems and Nanobiofluidics, Materials).
At C2N, the thesis work will be carried out in the Materials department's OXIDE team, which conducts research into crystalline oxide thin films, in collaboration with the Photonics department's MINAPHOT team, which works on silicon photonics.
All experimental facilities for the project are available in the C2N cleanroom, as are structural, optical and electrical characterizations in dedicated laboratories.

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