Public Thesis Defense of Yubin HUANG - IMCN/NAPS
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Thermal and thermoelectric transport properties in single MXene flakes
Friday October 3, 2025, 4pm - Room Mercator 02 - Place Louis Pasteur, 3 - 1348 Louvain-la-Neuve
MXenes are being increasingly explored for electronics at the micro and nanoscale. In recent years, their electrical, optical, mechanical, and electrochemical properties of single flakes have been gradually investigated. However, thermal and thermoelectric transport at the single-flake level remains largely unexplored. A fundamental understanding of local thermal and thermoelectric processes can inform the design of novel micro- and nano-devices and enhance their efficiency. In this thesis, the nanoscale thermal and thermoelectric transport properties of several types of MXenes, primarily Ti3C2Tx, are studied using the scanning thermal microscopy (SThM) technique. This method allows us to quantitatively measure the local thermal resistance and thermovoltage maps with a thermoresistive probe. First, thickness-dependent thermal transport from monolayer to few-layer MXene flakes is investigated. A diffusive thermal transport model is employed to extract the thermal conductivity and the thermal interface resistivity. An ultra-low thermal conductivity of 0.78 W m−1 K−1 in Ti3C2Tx MXene is observed, which is much lower than the value predicted by the Wiedemann–Franz (WF) law. The results reveal the underlying transport behavior and suggest the presence of strong electron–phonon interactions. Second, the layer-dependent thermoelectric properties are studied by stacking single-layer Ti3C2Tx layer-by-layer on the pre-patterned micro-bridge device. The interlayer interaction can lead to a change in the band structure and in turn result in a Seebeck coefficient change across the homostructures. Last, local thermoelectric mapping in MXene homostructures is performed using SThM in both AC (2ω method) and DC modes. The thermovoltage response along the junction is observed, and the corresponding Seebeck coefficient variation map is reconstructed using a deconvolution method. The high resolution thermovoltage maps demonstrate the influence of layer thickness, metallic contacts, local defects and surface terminations on the local Seebeck coefficient in MXene. This work aims to improve our understanding of local transport properties in single MXene flakes and to open new paths for designing high-performance devices with broader applications.
Jury Members :
Prof. Pascal Gehring (UCLouvain)(Supervisor)
Prof. Xavier Urbain (UCLouvain) (Chairperson)
Prof. Benoît Hackens (UCLouvain) (Secretary)
Prof. Jean-Christophe Charlier (UCLouvain)
Prof. Robert Szoszkiewicz (University of Warsaw, Poland)
Prof. Molina-Lopez Francisco (KU Leuven, Belgium)