Thermal boundary resistance at Si/Ge interfaces by molecular dynamics simulation

Abstract

In this study, we investigated the temperature dependence and size effect of the thermal boundary resistance at Si/Ge interfaces by non-equilibrium molecular dynamics (MD) simulations using the direct method with the Stillinger-Weber potential. The simulations were performed at four temperatures for two simulation cells of different sizes. The resulting thermal boundary resistance decreased with increasing temperature. The thermal boundary resistance was smaller for the large cell than for the small cell. Furthermore, the MD-predicted values were lower than the diffusion mismatch model (DMM)-predicted values. The phonon density of states (DOS) was calculated for all the cases to examine the underlying nature of the temperature dependence and size effect of thermal boundary resistance. We found that the phonon DOS was modified in the interface regions. The phonon DOS better matched between Si and Ge in the interface region than in the bulk region. Furthermore, in interface Si, the population of low-frequency phonons was found to increase with increasing temperature and cell size. We suggest that the increasing population of low-frequency phonons increased the phonon transmission coefficient at the interface, leading to the temperature dependence and size effect on thermal boundary resistance.

Predicting interfacial thermal resistance by machine learning

“…The mode of phonon transfer changes based on the interfacial conditions, and the PDOSs of the two materials forming the interface shift to reduce mismatch between the materials, thereby improving the thermal conductance. 94,95 Thus, the interfacial conditions which become important especially at or above the room temperature should be further considered in the model. In order to enhance the machine predictive power based on the known knowledge, we further considered the interfacial properties and categorized these properties into three descriptor sets (property descriptors, compound descriptors, and process descriptors), as shown in Fig.…”

“…4 The change in phonon transmission probability at the interface corresponds to the change in thickness. 60,94 The interlayer reflects whether an interlayer is present between the materials at the interface; it is assigned a value of either 1 (if an interlayer is present) or 0 (if no interlayer is present). In many cases, the adhesion layer, a naturally or thermally formed oxidation layer, and surface plasma treatment will form interlayers or a mixed region between the materials instead of a clear interface.…”

“…99 In other words, the interfacial serves as a coupling layer to tune the phonon transport mode and DOS, particularly when the interfacial film has mediating vibrational properties. 94 Moreover, the interlayers or materials with mediating properties along the heat flux may possibly enhance the channels for thermal conductance. 95 After selecting the descriptors, the three descriptor sets were used to train and generate the predictive models.…”

Molecular dynamics simulations of the effect of shape and size of SiO2 nanoparticle dopants on insulation paper cellulose

“…[1][2][3][4] In recent years, molecular dynamics simulations have been used to investigate the properties of polymers doped and modified by nanoparticles. [5][6][7][8][9][10][11][12][13] Simulations have demonstrated improvements in the mechanical properties of modified polymer materials, with the incorporation of smaller nanoparticles tending to yield larger increases in the Young's modulus. Incorporating nanoparticles can reportedly also improve the breakdown voltage and thermal stability of insulating materials.…”

Thermal boundary resistance at Au/Ge/Ge and Au/Si/Ge interfaces

“…Many theoretical studies have been performed to investigate the effects of heat ow direction, lm thickness, and period length on TBR in superlattice systems, and also the effects of interfacial properties, such as interfacial mixing, structural disorder, dislocation, roughness, and bonding strength on TBR. [33][34][35][36][37][38][39][40][41][42] However, the investigation of the effects of crystalline state of thin lms on TBR were limited. In this study we showed that the crystalline state of thin lms could affect TBR signicantly.…”