Controlled colloidal synthesis of SnS and SnSe nanosheets: growth mechanisms and thickness-dependent ferroelectric properties

This PhD project aims to develop a controlled colloidal synthesis of ultrathin two-dimensional nanosheets of tin sulfide and tin selenide (SnS and SnSe), with thickness precisely tuned from one to ten atomic layers. These layered van der Waals chalcogenides exhibit emerging electronic, optical, and ferroelectric properties at the nanoscale, offering strong potential for applications in nanoelectronics, sensors, ferroelectric devices, and energy conversion. The main objective is to finely control nucleation and anisotropic growth in order to obtain high-crystallinity nanosheets with well-defined morphology and uniform thickness distribution.

The strategy relies on optimizing colloidal chemistry using tin and chalcogen precursors, by adjusting temperature, ligand nature, solvents, reaction kinetics, and injection conditions. These parameters will be tuned to promote selective two-dimensional growth while limiting the formation of three-dimensional particles. The comparative study of SnS and SnSe, which are isostructural but chemically distinct, will help clarify the role of the chalcogen in growth mechanisms and in the emergence of ferroelectric properties.

Nucleation and growth mechanisms will be investigated through in situ liquid-cell electron microscopy (LCEM), enabling real-time monitoring of nanosheet formation. The synthesized materials will be characterized using complementary techniques: Raman spectroscopy and X-ray diffraction (XRD) to identify crystalline phases; atomic force microscopy (AFM) to accurately measure thickness; transmission electron microscopy (TEM, HRTEM, STEM-HAADF) and electron diffraction to analyze morphology and structure at the nanoscale; and EELS or EDX spectroscopy for chemical composition. Optical measurements (UV–Vis absorption and photoluminescence) will further probe electronic properties.
Ferroelectric properties will be locally investigated by piezoresponse force microscopy (PFM) and low-energy electron microscopy (LEEM) to map spontaneous polarization, ferroelectric domain structures, and switching mechanisms as a function of thickness. Together, these characterizations will establish detailed relationships between synthesis conditions, crystal structure, dimensions, and functional performance.
By combining colloidal synthesis, multiscale characterization, and in situ analysis, this project will provide fundamental insights into the formation mechanisms of 2D tin chalcogenides and into structure–property relationships. The knowledge gained will enable optimization of these ferroelectric materials for integration into next-generation nanoelectronic devices

MONARIS is a leading research laboratory in physical chemistry, affiliated with the Chemistry and Physics departments of the Faculty of Science and Engineering at Sorbonne Université.

The lab aims to advance the fundamental understanding of chemical reactivity across scales, combining cutting-edge experimental techniques with state-of-the-art theoretical modeling. Its research focuses on nanophased systems, exploring how chemical bonding governs the organization and response of matter to external stimuli.

Spanning from molecules to supramolecular assemblies and nano-objects, MONARIS addresses major societal challenges, including environmental transition, atmospheric chemistry, energy, nanotechnologies, and cultural heritage preservation.

The laboratory is also expanding its activities in astrophysics, astrochemistry, and atmospheric sciences, fostering strong national and international collaborations.

At the interface of experiment and theory, MONARIS provides a highly interdisciplinary and stimulating environment for research and innovation.

This project is intended for candidates holding a Master’s degree in chemistry, physical chemistry, or materials science, with a solid background in materials chemistry and physicochemistry. Experience or a strong interest in the colloidal synthesis of nanomaterials will be appreciated, as well as skills in structural and morphological characterization techniques (e.g., Raman spectroscopy, AFM and/or TEM).

The candidate should demonstrate strong experimental rigor, autonomy, and good proficiency in scientific English.

Required French level: Pre-intermediate – ability to communicate and be understood using simple messages in everyday situations.
Required English level: Upper-intermediate – ability to use the language effectively and express ideas clearly and accurately.