Tuning interfacial thermal conductance by combining single vacancy and atomic mass variation in crystalline and amorphous interface

Interfacial thermal resistance critically limits heat dissipation in nanoscale semiconductor devices. Although varying atomic mass and introducing vacancy defects in interface have each been shown to enhance interfacial thermal conductance (ITC), their combined effect remains unclear. On the other hand, vacancy defects are commonly observed in experiments during sample and device preparation. In this work, the influence of a single vacancy on the ITC of crystalline and amorphous interface with atomic mass variation between Si and Ge is investigated using the mode-resolved atomistic Green's function method. For amorphous interfaces, the ITC exhibits a single maximum as the atomic mass varies, while the introduction of a single vacancy consistently reduces the ITC by suppressing phonon transmission in the medium (3-4 THz) and high (8-9 THz) frequency ranges, and the location of the single vacancy has a relatively minor effect on the ITC. In contrast, for crystalline interfaces, a single vacancy can further enhance the ITC on top of the improvement achieved by varying atomic mass alone. The enhancement strongly depends on the vacancy location and atomic mass in the interface, with maximum ITC obtained at atomic mass value of 68 amu and 32 amu for vacancy in the left and right regions, respectively. Spectral and modal analyses reveal that vacancy enhance medium (4-5 THz) and high (8-10 THz) frequency phonon transmission, whereas low-frequency (<3 THz) phonons are weakly affected. Particularly, single vacancy in the crystalline interface can enhance interfacial thermal transport when the atomic mass at the interface takes unfavorable values. These results provide physical insight and design guidance for engineering high-ITC interfaces in semiconductor heterostructures.