Spatio-temporal Strain Analysis and Thermal Transport Modulation in Plastically Deformed InSe van der Waals Crystals

Contrary to typical inorganic semiconductors and functional materials with brittleness, InSe van der Waals crystals show remarkable room-temperature plasticity. Uncovering the mechanisms for the exceptional plasticity is of ultimate importance, and highly relies on the comprehension of strain state during deformation, which, however, remains an unresolved challenge. Moreover, the plastic deformation versus transport (e.g., thermal conductivity) correlation is yet to be quantitatively rationalized in these materials. Here, by using the digital-image-correlation (DIC) technique, we depict and analyze the spatio-temporal strain in InSe upon compression, providing straight evidence for the interlayer and cross-layer glides. Dense dislocations and grain boundaries are found to be created upon compression. As a result, the thermal conductivities are greatly reduced after plastic compression, being as low as 0.64 W/m K at room temperature and 0.38 W/m K at 600 K in a 50 % compressed specimen. Such a damped heat transport is well rationalized by incorporating the roles of multiple nanoscale defects as phonon scattering centers. This study provides new insight into the deformation mechanisms of 2D vdW crystals and shows that plastic deformation can be a powerful approach to modulate thermal properties of inorganic semiconductors for promising applications in energy utilization and heat management.