Shuang Tian

Interfacial thermal resistance due to vibrational mismatch remains a key challenge in thermal management. While crystalline interlayers are known to enhance thermal conductance, the potential of amorphous interlayers remains underexplored. Using non-equilibrium molecular dynamics simulations, we examine how mass distribution in amorphous interlayers affects interfacial thermal conductance (ITC) between Si and Ge. Compared to crystalline interlayers, amorphous ones generally show lower ITC, except under strong vibrational mismatch (e.g., 5 amu mass). This enhanced performance is attributed to the increased phonon density of states overlap and the broadened interfacial mode spectrum induced by amorphous disorder, which collectively facilitate both elastic and inelastic phonon transport. Notably, ITC peaks at 10 amu and exhibits a plateau over a range of masses—distinct from the sharp peaks of crystalline systems. Such plateau behavior can be attributed to a competing interplay between increased elastic contributions and suppressed inelastic transport as the interlayer mass increases. Our findings offer guidance for optimizing ITC in amorphous semiconductor interfaces.

Coherent phonons can give rise to phenomena and physical mechanisms in different systems. Understanding phonon-boundary scattering is critical for the manipulation of thermal properties. In this paper, it is found that the thermal conductivity of rough graphene nanoribbon first monotonically changes, and then exhibits an oscillatory manner with the varying of surface boundary roughness. An obvious increase in thermal conductivity, up to 25.33%, can be observed as surface boundary roughness increases from 0.61 to 0.72. This is in contrast to the conventional understanding that thermal conductivity typically decreases when surface boundary roughness increases. Further, a frequency-resolved picture and lattice dynamics analysis identify that the anomalous boundary effect originates from the coherent nature of phonons, which results in the roughness-selected destructive interference of different modes. Besides, the oscillation will be reduced by introducing rough boundaries with different sinusoidal shapes, which increases the randomness. This abnormal boundary effect can also be extended to other materials, for example, hexagonal boron nitride monolayer, depending mainly on the anharmonicity. The study reveals physical insights into phonon-boundary scattering and may aid the design of heat management and thermoelectric devices based on the boundary effect.

The high increase in interface density has become the main bottleneck for heat dissipation in gallium nitride/aluminum nitride (AlN)/silicon carbide (SiC) based nanodevices. In this paper, the interfacial thermal conductance (ITC) of AlN/SiC interface is investigated by non-equilibrium molecular dynamics simulation. It is found that introducing amorphous layers at AlN/SiC interface will result in an enhancement of its ITC by 2.32 times. Three different amorphous layers are investigated and can be achieved by fast thermal annealing. Among them, the amorphous SiC layers work best, and the amorphous AlN layers work worst. Further spectral analysis reveals that the enhancement of ITC comes from the strengthening of interfacial inelastic phonon processes, which boosts the transport of modes at a wide frequency range. What is more, as the thickness of amorphous layers increases, the enhancement of ITC weakens. This research provides a highly operational strategy to enhance ITC and enriches our understanding of inelastic phonon process at interface.

Utilizing surface roughness to manipulate thermal transport has aided important developments in thermoelectrics and heat dissipation in microelectronics. In this paper, through a multiparticle Lorentz gas model, it is found that thermal conductivity oscillates with the increase of surface roughness, and the oscillating thermal conductivity gradually disappears with the increase of nonlinearity. The transmittance analyses reveal that the oscillating thermal conductivity is caused by localized particles due to boundary effects. Nonlinearity will gradually break the localization. Thus, localization still exists in the weak nonlinear system, where there exists an interplay between nonlinear interaction and localization. Furthermore, it is also found that boundary shapes have a great influence on the oscillating thermal conductivity. Finally, we have also studied the oscillating thermal rectification effects caused by rough boundaries. This study gains insight into the boundary effect on thermal transport and provides a mechanism to manipulate thermal conductivity.