Understanding orientation dependent phonon transport is essential for optimizing heat dissipation in crystalline heterostructures for advanced electronic applications. However, the intrinsic and extrinsic mechanisms governing the degree of orientation dependent interfacial thermal conductance ($G$) remain insufficiently understood. Here, we systematically elucidate the fundamental mechanisms of orientation dependent heat transport across $\mathrm{Al}/\alpha \text{−}\mathrm{A}{\mathrm{l}}_2{\mathrm{O}}_3$ interfaces based on ultrafast pump-probe thermal conductance measurements and nonequilibrium molecular dynamics (NEMD) simulations. For nonideal $\mathrm{Al}/\alpha \text{−}\mathrm{A}{\mathrm{l}}_2{\mathrm{O}}_3$ interfaces prepared by thermal evaporation or magnetron sputtering, we observe only a weak orientation dependence in $G$, while intrinsic $\mathrm{Al}/\alpha \text{−}\mathrm{A}{\mathrm{l}}_2{\mathrm{O}}_3$ interfaces reveal a strong dependence, with a conductance ratio of approximately 1.8−2.4 across different crystallographic orientations. We attribute this intrinsic orientation dependence to anisotropy in phonon group velocity, i.e., the phonon focusing effect. In contrast, we demonstrate that the suppressed orientation dependent $G$ in nonideal $\mathrm{Al}/\alpha \text{−}\mathrm{A}{\mathrm{l}}_2{\mathrm{O}}_3$ interfaces results from an ultrathin amorphous layer on $\alpha \text{−}\mathrm{A}{\mathrm{l}}_2{\mathrm{O}}_3$ surfaces prior to Al deposition. This ultrathin amorphous layer acts as an isotropic filter, masking the angular dependence of phonon transmission from $\alpha \text{−}\mathrm{A}{\mathrm{l}}_2{\mathrm{O}}_3$ to Al, effectively obscuring the role of interfacial bonding strength. Furthermore, the weak orientation dependence persists down to 80 K, indicating that the amorphous layer strongly influences phonons transport across the entire frequency spectrum, including the low-frequency modes. This work advances the understanding of orientation dependent interfacial heat transport in nonideal metal/semiconductor interfaces, and thus is beneficial to the thermal management for crystalline heterostructures electronics devices.

Close

PrevNext

View figure in article

• Heat transfer
• Phonons
• Thermal boundary conductance
• Thermal properties
• Disordered systems
• Interfaces
• Solid-solid interfaces