Epitaxy Study of the Cobalt-Tin-Sulfur System - Towards Weyl Semi-Metal Co3Sn2S2 Thin Films
(2026)
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- Material advances driven by the understanding and design of microscopic phe- nomena are a key enabler for next-generation energy management applica- tions. Compounds formed by cobalt, tin, and sulfur are of particular interest in this context. Binary compounds within this system are relevant across mul- tiple 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. Molec- ular 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 re- ported 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 epi- taxy. 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.
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Rohde, M. (2026). Epitaxy Study of the Cobalt-Tin-Sulfur System - Towards Weyl Semi-Metal Co3Sn2S2 Thin Films. https://hdl.handle.net/2078.5/273432