Thermal Transport and Anharmonic Phonon Dynamics in Substrate-dependent MoSe ₂ Thin Films

Thermal dissipation efficiency represents a primary constraint on the power scalability of electronic and optoelectronic platforms that employ two-dimensional van der Waals semiconductors. Here, we introduce a systematic optothermal Raman study of large-area, few-layer MoSe 2 thin films grown by chemical vapor deposition on technologically relevant Si and SiO 2 substrates. Temperature-dependent Raman spectroscopy reveals strong anharmonic phonon behavior, accurately described by a unified model that includes the lattice thermal expansion effect and three-phonon and four-phonon scattering processes. Concurrently, Raman line width analysis provides direct access to substrate-dependent phonon lifetimes. By correlating Raman spectral evolution with varying temperature and optical power, we extract both the in-plane thermal conductivity and interfacial thermal conductance of supported MoSe 2 films, yielding room-temperature values of ∼32 ± 2 W m –1 K –1 for MoSe 2 /Si and ∼22 ± 4 W m –1 K –1 for MoSe 2 /SiO 2, along with corresponding interfacial thermal conductance values of ∼8.775 ± 0.125 MW m –2 K –1 and ∼5.335 ± 0.165 MW m –2 K –1, respectively. Complementary power-dependent photoluminescence measurements establish a direct link between thermal dissipation efficiency and excitonic recombination dynamics, showing enhanced exciton-dominated radiative emission on Si and increased phonon-assisted nonradiative losses on SiO 2 . These results define an integrated phonon-thermal-optoelectronic framework and identify substrate engineering as a key strategy for achieving thermally robust, high-power, and scalable two-dimensional optoelectronic and photonic devices.