“…A similar effect of the temperature elevation on Kaptiza resistance was observed for graphene-boron nitride hetero-nanosheets in the works done by Eshkalak et al . 47 and Liu et al 48 . Figure 7 The changes in Kapitza thermal resistance of six constructed grain boundaries A 1 (5–7–6–6–s), A 2 (5–7–6–s), A 3 (5–7–5–7–s), A 4 (5–7–6–6–a), A 5 (5–7–6–a), and A 6 (5–7–5–7–a) in BC 3 GrHs as a function of temperature at ΔT = 40 K and zero strain.…”
Simulation of thermal properties of graphene hetero-nanosheets is a key step in understanding their performance in nano-electronics where thermal loads and shocks are highly likely. Herein we combine graphene and boron-carbide nanosheets (BC3N) heterogeneous structures to obtain BC3N-graphene hetero-nanosheet (BC3GrHs) as a model semiconductor with tunable properties. Poor thermal properties of such heterostructures would curb their long-term practice. BC3GrHs may be imperfect with grain boundaries comprising non-hexagonal rings, heptagons, and pentagons as topological defects. Therefore, a realistic picture of the thermal properties of BC3GrHs necessitates consideration of grain boundaries of heptagon-pentagon defect pairs. Herein thermal properties of BC3GrHs with various defects were evaluated applying molecular dynamic (MD) simulation. First, temperature profiles along BC3GrHs interface with symmetric and asymmetric pentagon-heptagon pairs at 300 K, ΔT = 40 K, and zero strain were compared. Next, the effect of temperature, strain, and temperature gradient (ΔT) on Kaptiza resistance (interfacial thermal resistance at the grain boundary) was visualized. It was found that Kapitza resistance increases upon an increase of defect density in the grain boundary. Besides, among symmetric grain boundaries, 5–7–6–6 and 5–7–5–7 defect pairs showed the lowest (2 × 10–10 m2 K W−1) and highest (4.9 × 10–10 m2 K W−1) values of Kapitza resistance, respectively. Regarding parameters affecting Kapitza resistance, increased temperature and strain caused the rise and drop in Kaptiza thermal resistance, respectively. However, lengthier nanosheets had lower Kapitza thermal resistance. Moreover, changes in temperature gradient had a negligible effect on the Kapitza resistance.
“…A similar effect of the temperature elevation on Kaptiza resistance was observed for graphene-boron nitride hetero-nanosheets in the works done by Eshkalak et al . 47 and Liu et al 48 . Figure 7 The changes in Kapitza thermal resistance of six constructed grain boundaries A 1 (5–7–6–6–s), A 2 (5–7–6–s), A 3 (5–7–5–7–s), A 4 (5–7–6–6–a), A 5 (5–7–6–a), and A 6 (5–7–5–7–a) in BC 3 GrHs as a function of temperature at ΔT = 40 K and zero strain.…”
Simulation of thermal properties of graphene hetero-nanosheets is a key step in understanding their performance in nano-electronics where thermal loads and shocks are highly likely. Herein we combine graphene and boron-carbide nanosheets (BC3N) heterogeneous structures to obtain BC3N-graphene hetero-nanosheet (BC3GrHs) as a model semiconductor with tunable properties. Poor thermal properties of such heterostructures would curb their long-term practice. BC3GrHs may be imperfect with grain boundaries comprising non-hexagonal rings, heptagons, and pentagons as topological defects. Therefore, a realistic picture of the thermal properties of BC3GrHs necessitates consideration of grain boundaries of heptagon-pentagon defect pairs. Herein thermal properties of BC3GrHs with various defects were evaluated applying molecular dynamic (MD) simulation. First, temperature profiles along BC3GrHs interface with symmetric and asymmetric pentagon-heptagon pairs at 300 K, ΔT = 40 K, and zero strain were compared. Next, the effect of temperature, strain, and temperature gradient (ΔT) on Kaptiza resistance (interfacial thermal resistance at the grain boundary) was visualized. It was found that Kapitza resistance increases upon an increase of defect density in the grain boundary. Besides, among symmetric grain boundaries, 5–7–6–6 and 5–7–5–7 defect pairs showed the lowest (2 × 10–10 m2 K W−1) and highest (4.9 × 10–10 m2 K W−1) values of Kapitza resistance, respectively. Regarding parameters affecting Kapitza resistance, increased temperature and strain caused the rise and drop in Kaptiza thermal resistance, respectively. However, lengthier nanosheets had lower Kapitza thermal resistance. Moreover, changes in temperature gradient had a negligible effect on the Kapitza resistance.
“…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 lattice vibration mismatch. In addition, topological defects, 7 doping and interface topography optimization 33 were employed to effectively improve the thermal energy transport across the in-plane Gr/h-BN heterostructure interface. These previous studies have enriched our understanding of the interfacial thermal transport properties of Gr/h-BN heterostructure.…”
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
“…Since the zigzag interfaces with either boron–carbon or nitrogen–carbon links have smaller formation energy values than that of the armchair interface, the former is more likely formed. Researchers have mostly focused on the heat transfer of graphene/h-BN in-plane heterostructures with zigzag interfaces [ 24 , 25 , 26 ]. However, the graphene/h-BN in-plane heterostructures with armchair interfaces have also been prepared in experiments [ 15 ], and they show a higher bandgap as compared to the pristine nanoribbons [ 17 , 27 ].…”
Based on nonequilibrium molecular dynamics (NEMD) and nonequilibrium Green’s function simulations, the interfacial thermal conductance (ITC) of graphene/h-BN in-plane heterostructures with near-interface defects (monovacancy defects, 585 and f5f7 double-vacancy defects) is studied. Compared to pristine graphene/h-BN, all near-interface defects reduce the ITC of graphene/h-BN. However, differences in defective structures and the wrinkles induced by the defects cause significant discrepancies in heat transfer for defective graphene/h-BN. The stronger phonon scattering and phonon localization caused by the wider cross-section in defects and the larger wrinkles result in the double-vacancy defects having stronger energy hindrance effects than the monovacancy defects. In addition, the approximate cross-sections and wrinkles induced by the 585 and f5f7 double-vacancy defects provide approximate heat hindrance capability. The phonon transmission and vibrational density of states (VDOS) further confirm the above results. The double-vacancy defects in the near-interface region have lower low-frequency phonon transmission and VDOS values than the monovacancy defects, while the 585 and f5f7 double-vacancy defects have similar low-frequency phonon transmission and VDOS values at the near-interface region. This study provides physical insight into the thermal transport mechanisms in graphene/h-BN in-plane heterostructures with near-interface defects and provides design guidelines for related devices.
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