Thèse

  • (en anglais) Crystalline oxide epitaxy for silicon photonics

    A partir de octobre 2024

    Thomas Maroutian

    thomas.maroutian@c2n.upsaclay.fr - +33 1 70 27 04 89

    Département Photonique', 'Materiaux

    Thèse

    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.
    Scientific project:
    The project will focus on the growth of doped zirconia (ZrO2) thin films on single crystal substrates, and in particular on the study of the interplay between dopant and substrate-induced strain to stabilize a ferroelectric phase of ZrO2 at 50 nm thickness or more. Stimulating results [1,2,3,4] have already been obtained in this respect at C2N with ZrO2 films grown by pulsed laser deposition (PLD), paving the way for the study of dopant-engineering. A new molecular beam epitaxy (MBE) system has been commissioned at the beginning of 2024 to allow for a better control of dopant and oxygen stoichiometry in these compounds.

    All the experimental facilities for the 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 ERC Advanced Grant CRYPTONIT on doped crystalline oxides for silicon photonics.

  • (en anglais) Innovative characterisation methods for tandem photovoltaic cells

    A partir de septembre 2024

    Amaury Delamarre

    amaury.delamarre@c2n.upsaclay.fr - 01 70 27 04 80

    Département Photonique

    Thèse

    The Institute :
    The Centre for Nanosciences and Nanotechnology (C2N) is a joint research unit between the CNRS and Université Paris-Saclay. The center develops research in the fields of material science, nanophotonics, nanoelectronics, and nanotechnologies, covering all the range from fundamental to applied sciences. The PhD thesis offered here will take place in the Sunlit Team, which develops innovative approaches for solar cells, aiming at high efficiencies, cost reduction and reliability of the devices.
    Scientific project:
    Photovoltaic is playing a major role in the energy transition, and its share in electricity generation is expected to continue rising to contribute to the net zero emission goals by 2050. 90 % of the currently produced solar panels are using silicon solar cells with gradually decreasing costs and increasing efficiency. Nevertheless, this efficiency is nearing its physical limit of 29.4 %, with 26.8 % obtained in laboratory. In order to overcome this limit, the next generation of solar cells will consist in tandem devices, that combine two materials of different bandgaps. In our laboratory and close partners in particular, III-V on silicon and perovskite on silicon devices are being produced.
    Those new devices present exciting challenges: new fabrication steps, new materials and combinations of materials, new aging mechanisms and failure modes… All those aspects call for a better understanding of their working principles, through new characterization methods and data analysis. We propose in this thesis to take advantage of the recognized know-how of the C2N and partners, in terms of device characterization and state-of-the-art equipment.
    Existing methods will be used, and new ones will be developed. In particular, an innovative approach will be considered, based on simultaneous electrical and optical carrier injection in solar cells, with which we showed that we can access the current collection efficiency in each subcells, with a spatial resolution. A rich variety of solar cells will be investigated (with III-V, silicon, perovskites, and their combination, with and without accelerated degradation), thanks several collaborators.This thesis comprises an extensive part of experimental work in the laboratory as well as data treatment. We expect the PhD candidate to propose further developments of the techniques already existing at the laboratory, as well as to suggest the exploration of new methods. He / she will propose models to explain the observed phenomena, and design experiments for their validation, using his / her own knowledge as well as the scientific literature. He / she will take advantage of the unique luminescence characterization platform of the partner laboratories as well as complementary methods (solar simulator, quantum efficiency). This environment will provide the intern various opportunities to tackle this project challenge and gain experience.


    Profile:
    The candidate must possess solid knowledges in material physics and characterization. He must show good project management skills, for the development of measurement procedures involving numerous parameters. He will be able to work independently and suggest innovative solutions to reach the project objectives. Collaborative work being at the core of the program, communication skills are required for team working as well as regular presentation of work progress in internal meetings.

    More information in the attached file

     

     

  • (en anglais) Design of a high efficiency voltage converter for HIFU

    A partir de mars 2024

    Ming Zhang

    ming.zhang@c2n.upsaclay.fr - 01 70 27 05 20

    Département Microsyst

    Thèse

    High Intensity Focused Ultrasound (HIFU) is a very promising treatment tool and will be increasingly used in the years to come. Compared to conventional treatments, HIFU-based treatments have enormous advantages: non-invasive, reduced side effects and a selective treatment area. The combination between the use of HIFU and conventional approaches can only bring more effectiveness. By exploiting the thermal effect of HIFU, a local rise in temperature at the focal point of the ultrasound emitted allows the ablation of the cancer cell. In this context, we have proposed a research project, which benefits a funding from the national research agency (ANR).
    In this PhD study, which is part of this research project and is funded by the ANR, the design of an oscillating voltage converter with high energy conversion efficiency will be requested. An exhaustive search of converter structures published in the literature will be the first step to consider. Based on the structures deemed exploitable, an in-depth analysis will be carried out in order to distinguish the advantages and disadvantages of different structures and to identify the possibility of exploiting them for our application. Electrical simulations of the selected structures will make it possible to quantify the performance of different structures.
    An improvement in performance or even a proposal for an innovative structure will always be part of the expected results of a research project. In order to verify the performance obtained from the designed circuits, PCB (Printed Circuit Board) designs will be implemented, tested and evaluated before further investigations for optimization design.
    This PhD study will be carried out in the C2N laboratory (Center of Nanosciences and Nanotechnologies, Palaiseau, France). Potential candidates are asked to send a CV accompanied by M2 grades or equivalent to Ms. Ming Zhang).

    More specific requests for candidates: good knowledge of electronics is desired and good English level will be appreciated. Some experience with CAD tools such as Cadence,
    Spice, Altium Designer will be welcome.

  • (en anglais) Magneto-optical circulator : from design to experimental demonstration

    A partir de janvier 2024

    Béatrice Dagens

    beatrice.dagens@c2n.upsaclay.fr - 01 70 27 04 07

    Département Photonique

    Thèse

    consult the offer in attached file