Delayed Thermal Relaxation in Lateral Heterostructures of Transition-Metal Dichalcogenides

: Recent experimental advances have paved the way for the synthesis of a wide range of transition-metal dichalcogenides (TMDs) and nanoengineering in terms of combining TMDs of different compositions in the same planar structure. Due to numerous suggested optoelectronic applications of these materials, the in-plane heat dissipation of such lateral heterostructures is investigated via molecular dynamics (MD). A broad range of pure and heterostructural TMDs have been considered in terms of the metal (Mo or W) and the chalcogenide (S or Se) combinations. In our MD simulations, we thermally excite the central region of the samples and then allow the excitation to dissipate and reach thermal equilibrium. We observe nonexponential relaxation processes, which are quantified in terms of a characteristic relaxation time. The heat dissipation of bilayer heterostructures is substantially enhanced compared to the single-layer ones. Phonon spectra mismatches among the interfacial and bulk atoms lead to the manifestation of a high barrier for phonon propagation across the boundary of the heterostructure, enhancing the characteristic thermal relaxation times by up to an order of magnitude. The sharpness of the heterostructure interface boundaries plays an important role as well, and it is of major importance when considering applications and the limitations of designing these materials.