Ferroelectric materials, with their high dielectric constant and spontaneous polarisation, are the subject of intense research in microelectronics. Polarisation is an essential parameter for these materials while its characterization remains mainly limited to the macroscopic scale by conventional electrical methods. To deepen the understanding of these materials, particularly in thin layers, and built new devices, local measurements are essential. This thesis project aims to develop a new methodology to directly map polarisation in devices at nanoscale. By combining the expertise of SPEC in thin film growth and of C2N in nanostructuration and electric measurements, we will elaborate and design a particular geometry of nanostructures allowing the use of operando electronic holography (collaboration with CEMES-CNRS, ANR POLARYS) to quantitatively map the local electrical potential in nanodevices upon application of a voltage.