Description of the thesis topic

Silicon photonics, i.e. the use of Si for integrated circuits, has emerged industrially more than a decade ago and is now a well-established technology. For future communication networks, new challenges have to be considered in terms of speed, power consumption, flexibility, and reliability. At C2N, we are currently exploring a new paradigm for advanced photonic circuits based on the hybrid integration of crystalline oxides in the silicon photonics platform for the telecom wavelength range (1.3µm-1.55µm). This will provide several physical properties non-existent in Si, such as ferroelectricity, and thus enable advanced nonlinear and optoelectronic devices.

The project will focus on the integration of perovskite oxide thin films for silicon photonics. In particular, the oxide of choice is KTaNbO3 (KTN) with record high electro-optic coefficients in bulk form. The challenge is first to obtain it with same outstanding properties in thin film form, and then to integrate it in photonic test devices with low optical losses. The path chosen for the project is to grow high quality single crystalline films on oxide substrates, and to transfer them on silicon through the use of sacrificial layers.
The PhD at C2N will take advantage of metalorganic molecular beam epitaxy (MO-MBE) to study different sacrificial layers on oxide substrates such as sapphire (Al2O3) and lithium niobate (LiNbO3), as well as different orientations and symmetries of perovskite oxide buffer layers such as SrTiO3 on silicon. The KTN thin films will be deposited in collaboration with laboratories in France and Germany, and C2N will then characterize the crystalline quality and optical properties of the films on silicon (buffer layer approach) or after transfer (sacrificial layer approach). The micro-transfer printing technique will be developed for the oxide layers of the project, in order to allow for a precise positioning of transferred layers on photonic test devices.

All the experimental facilities for the PhD project are available in C2N cleanroom, together with the tools for structural, optical, and electrical characterizations of the samples in dedicated labs.

The work is part of the European MSCA HINA project on the Hybrid integration of alkaline niobate-tantalate films for advanced photonic and piezoelectric devices.

Work Context

The PhD thesis project will be carried out at the Centre for Nanoscience and Nanotechnology (C2N, Palaiseau, France), as part of the OXIDE team in the Materials Department. The team conducts research into oxide crystalline thin films integrated into electronic and photonic devices, such as planar capacitors, tunnel junctions and optical waveguides. Studies range from the growth of layers by epitaxy to their shaping and integration by cleanroom technology, and finally to characterizing and exploiting their physical properties in the resulting devices. For this thesis project, the integration part for silicon photonics will be carried out in close collaboration with the MINAPHOT team in C2N's Photonics department. Finally, in the framework of the European HINA project (Marie Sklodowska-Curie action), exchanges and stays in other laboratories involved in the project, notably in Germany, will be planned during the thesis.

The position is located in a sector under the protection of scientific and technical potential (PPST), and therefore requires, in accordance with the regulations, that your arrival is authorized by the competent authority of the MESR.

Constraints and risks

The experimental part of the thesis will be carried out in a cleanroom environment.