Mapping Hot Spots at Heterogeneities of Few-Layer Ti 3 C 2 MXene Sheets.

Structural defects and heterogeneities play an enormous role in the formation of localized hot-spots in 2D materials used in a wide range of applications from electronics to energy systems. In this report, we employ scanning thermal microscopy (SThM) to spatially map the temperature rise across various defects and heterogeneities of titanium carbide (Ti3C2Tx - T stands for surface terminations) MXene nanostructures under high electrical bias with sub-50-mK temperature resolution and sub-100-nm spatial resolution. We investigated several Ti3C2Tx flakes having different thicknesses as well as heterogeneous MXene structures incorporating line defects or vertical heterojunctions. High-resolution temperature rise maps allow us to identify localized hot-spots and to quantify the non-uniformity of the temperature fields across various morphological features. The results show that the local heating is most severe in vertical junctions of MXene flakes and is highly affected by non-uniform conduction due to the presence of line defects. These results provide a direct insight into the power dissipation of MXene-based devices and the roles of various heterogeneities that are inherent to the material synthesis process. This study provides a guideline that how a better understanding of the structure-property-processing correlations and further optimization of the synthesis routes could improve the lifetime, safety, and operation limits of the MXene-based devices.