Nanoscale charge transport in MXenes and their prospects for sensing applications
(2026)
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- (en) Although the use of MXenes in electronic applications has been increasingly reported, the understanding of charge transport in these materials remains at an early stage. In this thesis, charge transport mechanisms in Ti3C2Tx MXenes are investigated from the individual flake-scale to the flake network-scale, and their potential for gas sensing applications is examined. First, conductive atomic force microscopy (C-AFM) is employed to map local conductivity variations within individual flakes, revealing their large resistivity anisotropy. Beyond individual flakes, inter-flake junction resistance is characterized using four-probe scanning tunneling microscopy and C-AFM, evidencing junction-limited transport in Ti3C2Tx conductive paths. This conclusion is further supported by measurements on devices with metallic contacts directly patterned on the flakes. The same devices were also used to perform low-temperature transport measurements, showcasing the metallic nature of Ti3C2Tx and signatures of quantum interference at low temperatures. Next, the gas sensing properties of pristine Ti3C2Tx and its composites are studied in the framework of ppm-level ammonia detection. From these measurements, the sensing properties of Ti3C2Tx alone exhibit limited sensing performance, whereas composite materials benefit from synergistic effects that significantly enhance their sensing characteristics. More specifically, MoS2-Ti3C2Tx composites display increased response amplitudes and faster kinetics, while polyaniline-Ti3C2Tx composites demonstrate an improved response reproducibility, stability, and a reduction in sensing losses over time, compared to pristine polyaniline. Finally, ppm-level ammonia detection is demonstrated with these composites deposited on paper-based substrates, providing a more sustainable alternative to Si/SiO2 substrates.
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de Leuze, O. (2026). Nanoscale charge transport in MXenes and their prospects for sensing applications. https://hdl.handle.net/2078.5/276853