Missions

The researcher will be responsible for conducting research on MBE C-21 growth reactor, as well as associated characterizations (XRD, AFM, optical and electron microscopy, and electrical characterization).
The objective of the project is to evaluate the potential of NbN thin films grown epitaxially on silicon substrates for the production of superconducting quantum circuits. Epitaxy will be performed at CRHEA on an MBE reactor using ammonia as a nitrogen source. Niobium is evaporated using an electron gun cell. Highly resistive 2-3" Si(111) silicon substrates will be used.
The project will involve fabricating and characterizing superconducting resonators from Si/AlN/NbN heterostructures. Losses, quality factors, resistivities, and kinetic inductances will be measured. The influence of the thickness of the NbN layer on these different quantities will be studied. It will be particularly interesting to study how the resonator losses evolve as a function of the resistivity and therefore of the kinetic inductance. Indeed, by using epitaxially grown materials of high structural quality, we hope to be able to increase the kinetic inductance (via the reduction of the NbN thickness) without significantly degrading the quality factor of the resonator. We will also study the effect of surface oxidation of the superconducting NbN layer by implementing a surface passivation layer (amorphous silicon or epitaxially grown AlN). The influence of the stoichiometry of cubic NbN will also be studied. The fabrication and characterization of the superconducting resonators will be carried out at the ENS using its own resources. Note that the influence of the substrate and the AlN buffer layer will also be studied by working on epitaxially grown NbN layers on sapphire substrates, given that sapphire is the substrate commonly used by B. Huard's team. The material will be characterized at CRHEA using atomic force microscopy and X-ray diffraction.
The project will also focus on the NbN/AlN/NbN heterostructure for the creation of a Josephson junction. For this structure, the goal is to finely characterize the interfaces as well as the structural and chemical qualities of the three layers using transmission electron microscopy at CRHEA. The influence of the thicknesses of the AlN tunnel barrier and the two NbN electrodes on the quality of the heterostructure will be studied. The epitaxially grown material will enable CRHEA to develop expertise in the various stages of Josephson junction manufacturing. This work will allow us to identify in advance the potential difficulties linked to the manufacturing process on this stack. We will specifically study the etching selectivity between NbN and AlN which will obviously be a key step in the manufacturing of the Josephson junction.

Activités

- Develop and characterize suitable structures using molecular beam epitaxy
- Interact with the project partner

Compétences

Knowledge/Awareness: Knowledge of semiconductor physics, materials physics; knowledge of ultrahigh vacuum and materials characterization; sufficient level of English to interact with non-French-speaking colleagues.

Contexte de travail

The position is part of a project that aims to evaluate the potential of NbN thin films grown epitaxially on silicon substrates for the production of superconducting quantum circuits. This project will establish a collaboration between CRHEA (SEMI and QUANTIC teams) and ENS Lyon (Quantum Circuits Group) on an extremely dynamic topic.

Le poste se situe dans un secteur relevant de la protection du potentiel scientifique et technique (PPST), et nécessite donc, conformément à la réglementation, que votre arrivée soit autorisée par l'autorité compétente du MESR.