Understanding And Tuning The Heat Transport At Interfaces Between Metals And Highly Anisotropic Semiconductors.

A complete and accurate description of nanoscale heat transport processes is essential for understanding energy transfer mechanisms and advancing thermal management technologies. This dissertation explores, both theoretically and experimentally, the fundamental heat transport mechanisms in anisotropic semiconductors and investigates how ultrathin metallic interlayers influence thermal boundary conductance at metal-semiconductor interfaces.

We first examined metal-isotropic semiconductor systems and introduced a hybrid diffuse mismatch model to describe phonon-mediated interfacial heat transfer. Our thermal model, which incorporates multiple scattering pathways was validated using existing experimental data. It successfully captures how interfacial conductance can be tuned by interlayer thickness, even with films as thin as 1 nm.

To accurately characterize the metal-anisotropic semiconductor interface, we studied how in-plane thermal conductivity evolves with thickness in graphite, MoS₂, and hBN. Results showed that conductivity increases with thickness and plateaus at ~5 µm for graphite and ~500 nm for MoS₂ and hBN, reaching bulk values of 2000 W/mK, 114 W/mK, and 490 W/mK, respectively. These findings were interpreted using Boltzmann transport modeling.

We then extended the hybrid model to metal–anisotropic semiconductor interfaces and validated its predictions experimentally. The results emphasize the importance of accounting for full phonon dispersion, optical phonons, and electron-phonon coupling in accurately modeling interfacial heat transport. Our results provide a new insight into the fundamental physics of heat transport as well as offer ways to design materials and devices with tailored thermal properties for applications in nano- and micro-electronics, thermoelectrics and nanotechnology.