Combining both vertical and in-plane two-dimensional (2D) heterostructures opens up the possibility to create an unprecedented architecture using 2D atomic layer building blocks. The thermal transport properties of such mixed heterostructures, critical to various applications in nanoelectronics, however, have not been thoroughly explored. Herein, we construct two configurations of multilayer in-plane graphene/hexagonal boron nitride (Gr/h-BN) heterostructures (i.e. mixed heterostructures) via weak van der Waals (vdW) interactions and systematically investigate the dependence of their interfacial thermal conductance (ITC) on the number of layers using non-equilibrium molecular dynamics (NEMD) simulations. The computational results show that the ITC of two configurations of multilayer in-plane Gr/h-BN heterostructures (MIGHHs) decrease with increasing layer number n and both saturate at n = 3. And surprisingly, we find that the MIGHH is more advantageous to interfacial thermal transport than the monolayer in-plane Gr/h-BN heterostructure, which is in strong contrast to the commonly held notion that the multilayer structures of Gr and h-BN suppress the phonon transmission. The underlying physical mechanisms for these puzzling phenomena are probed through the analyses of heat flux, temperature jump, stress concentration factor, overlap of phonon vibrational spectra and phonon participation ratio. In particular, by changing the stacking angle of MIGHH, a higher ITC can be obtained due to the thermal rectification behavior. Furthermore, we find that the ITC in MIGHH can be well-regulated by controlling the coupling strength between layers. Our findings here are of significance for understanding the interfacial thermal transport behaviors of multilayer in-plane Gr/h-BN heterostructure, and are expected to attract extensive interest in exploring its new physics and applications. Graphene/hexagonal boron nitride (Gr/h-BN) heterostructure, which benefits from the small lattice mismatch between Gr and h-BN, has been successfully synthesized both vertical 22 -24 and coplanar 2 , 25 , 26 configurations, paving the way for constructing the mixed heterostructures. In parallel to the efforts on pursuing a more sophisticated synthesis method, the interfacial thermal transport properties of Gr/h-BN heterostructure, which play a pivotal role in the high-performance thermal interface materials (TIMs) and heterostructures devices, 27 -29 are urgently needed to be understood. Accordingly, using a transient heating technique, Zhang et al. 30 showed that the interfacial thermal resistance in the vertical Gr/h-BN heterostructure is affected by interatomic bond strength, heat flux direction and functionalization. Relatively, Chen et al. 31 , 32 found that the in-plane Gr/h-BN heterostructure exhibits a negative differential thermal resistance behavior, which is caused by the phonon resonance effect and the

This study uses non-equilibrium molecular dynamics simulations to investigate the impact of antisite substitution on thermal conductivity. The phonon-dispersion curve and predicted thermal conductivity of pristine hexagonal boron nitride nanosheets (hBNNSs) show good agreement with the experiment results, indicating the reliability of the extep potential. It is clear that both neighboring substitution (NS) and random substitution (RS) drastically reduce the thermal conductivity of hBNNSs, of which RS has a larger effect. Calculations for the participation ratio and relaxation time show that the localization is the primary cause for the reduction in thermal conductivity when the defect concentration is low. When the defect concentration is higher, the primary cause is phonon-defect scattering in all phonon modes. RS has a larger effect on the phonon modes with long mean free paths, while NS has a larger effect on phonon modes with various lengths of mean free paths.

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Thermal resistance at a soft/hard material interface plays an undisputed role in the development of electronic packaging, sensors, and medicine. Adhesion energy and phonon spectra match are two crucial parameters in determining the interfacial thermal resistance (ITR), but it is difficult to simultaneously achieve these two parameters in one system to reduce the ITR at the soft/hard material interface. Here, we report a design of an elastomer composite consisting of a polyurethane−thioctic acid copolymer and microscale spherical aluminum, which exhibits both high phonon spectra match and high adhesion energy (>1000 J/m 2 ) with hard materials, thus leading to a low ITR of 0.03 mm 2 •K/W. We further develop a quantitative physically based model connecting the adhesion energy and ITR, revealing the key role the adhesion energy plays. This work serves to engineer the ITR at the soft/hard material interface from the aspect of adhesion energy, which will prompt a paradigm shift in the development of interface science.

This study uses non-equilibrium molecular dynamics simulation (NEMD) to investigate the effect of random vacancy defects on the in-plane thermal conductivity of borophene. phonon dispersion curves (PDC) and phonon group velocities areused to explain the anisotropy of the thermal conductivity of borophene nanosheets and the transmission characteristics of the acoustic and optical branches. Further calculations for the in-plane thermal conductivity of borophene with random vacancy defects are carried out, and the calculations show that the thermal conductivity gradually decreases to a steady state with increasing defect concentration. The phonon density of states (PDOS) and phonon participation rate (PR) are used to explain describe the activity of phonons in borophene for further explaining the change of thermal conductivity. Finally, the effect of defects on thermal conductivity is further verified by the spatial distribution of localized intensity of borophene nanosheets. Keywords:Borophene; In-plane thermal conductivity; Random vacancy defect; Phonon transport; Molecular dynamics

The in-plane graphene/hexagonal boron nitride (Gr/h-BN) heterostructures have received extensive attention in recent years due to their excellent physical properties and the development potential of next-generation nanoelectronic devices. Generally, different bonding types between Gr and h-BN are considered in different non-equilibrium molecular dynamics (NEMD) simulations studies. However, which type of bonding is most conducive to interface thermal transport is still very confusing. In this work, we investigate the interfacial thermal conductance (ITC) and the thermal rectification (TR) in five different bonding types of in-plane Gr/h-BN heterostructures by using NEMD simulations. It is found that the ITC depends strongly on the bonding strength and arrangement of different atoms across the boundary. Among the five different bonding types of heterostructures, the C-N bonded heterojunction exhibits the highest ITC due to its stronger interfacial bonding. The analyses on the strain distribution indicated that a low interfacial stress level at the interface junction, may facilitate the heat conduction, thus leading to a higher ITC. In addition, we found that TR occurs in all five bonded heterostructures, and the C-B bonded heterojunction possesses the highest TR factor. The present study is of significance for understanding the thermal transport behavior of Gr/h-BN heterostructures and promoting their future applications in thermal management and thermoelectric devices.