Public Thesis Defense of Michael ROHDE - IMCN/NAPS
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Epitaxy Study of the Cobalt-Tin-Sulfur System – Towards Weyl Semi-Metal Co3Sn2S2 Thin Films
Wednesday March 4th, 2026 - 3pm - MERC11 - Place Louis Pasteur, 3 - 1348 Louvain-la-Neuve
Material advances driven by the understanding and design of microscopic phenomena area key enabler for next-generation energy management applications. Compounds formed by cobalt, tin, and sulfur are of particular interest in this context. Binary compounds within this system are relevant across multiple fields, including passive and active heat management, energy storage, and catalysis. The ternary compound Co3Sn2S2 is a magnetic Weyl semimetal that exhibits record transverse thermoelectric benchmark values by harnessing both intrinsic magnetism and Berry curvature, making it a highly promising material for efficient active on-chip cooling. Device-level integration relies on controlled synthesis at the nanoscale. Molecular beam epitaxy is well known for its high degree of control, enabling the growth of high-quality crystalline thin films, yet it has been only scarcely reported for these materials. This is largely due to the challenge of navigating the relatively complex phase diagram and, in particular for Co3Sn2S2, achieving controlled sulfur incorporation. In this thesis, we address the synthesis of binary and ternary compounds in the cobalt-tin-sulfur system using sulfur plasma-assisted molecular beam epitaxy. Highly crystalline, epitaxial binary thin films (≈ 20 nm range) are realized and characterized with respect to both their individual applications and their role as guiding references for ternary synthesis. Building on these insights, the growth mechanism leading to a mixed-phase Co3Sn2S2 thin film is identified. This film exhibits signatures consistent with Co3Sn2S2 in magnetometry and transport measurements, demonstrating the validity of this growth approach and paving the way for further thermoelectric characterization.
Jury members
Prof. Pascal Gehring (UCLouvain) Supervisor
Prof. Francisco Molina-Lopez (KULeuven) Supervisor
Prof. Clement Merckling (KULeuven) Co-Supervisor
Prof. Xavier Gonze (UCLouvain) Chairperson
Prof. Benoit Hackens (UCLouvain) Secretary
Prof. Stefan De Gendt (KULeuven)
Prof. Brahim Dkhil (Universite Paris-Saclay)
Prof. Xavier Wallart (University of Lille)
Pay attention : the public defense of Michael ROHDE will also take place in the form of a videoconference