Divergent interfacial thermal transport in MoS2/Si heterostructure over optical phonon modes

Thermal transport within nanostructures is highly confined by interfaces, and non-trivial physics can emerge at boundaries. Theoretical studies have shown that different phonon modes can exhibit varying thermal resistances at interfaces. Experimental observation of these variations, however, is lacking. Using the steady-state Raman thermometry, the E2g1 and A1g vibrational modes of MoS2 were utilized to characterize the thermal transport properties across the MoS2/Si interface. Our results revealed distinct temperature rises associated with different modes, indicating various mode contributions in the interfacial thermal conductance. Combining experimental and numerical simulations, the out-of-plane mode in MoS2 was found to contribute less to the interfacial transport, by 21.5%, attributed to the less variational mode mismatch of the in-plane phonon, compared to the in-plane mode. Furthermore, our results confirmed a 26.9% higher thermal conductivity from the out-of-plane mode than the in-plane one.