Molecular dynamics simulation of heat transport across silicon-carbon nanotubes interface

Thermal interfacial resistance across single wall nanotube (SWNT) and silicon interface is investigated by molecular dynamics (MD) simulation. The effect of the interaction on thermal interfacial resistance is studied by applying bonded interaction as sum of bonded and non-bonded van der Waals interactions, and only non-bonded van der Waals interaction on the interface. For both cases, different temperature discontinuities (drops) at the interface are obtained. It is found that the thermal interfacial resistance of non-bonded interaction at the 3A separation is 20 times greater than that of the bonded interaction. At 300K, the thermal interfacial resistance of the bonded interaction is 2.85x10-9m2K/W and that of non-bonded interaction is 5.65x10-8m2K/W. It is also found that the thermal interface resistance decreases as temperature increases up to room temperature. The low frequency radial phonon modes in CNT are excited due to the coupling with silicon phonon modes and contribute the heat transport across interface under the bonded interaction. In contrast, no change of radial phonon mode in non-bonded interaction is found. The excitation of the radial breath mode (RBM) and low frequency radial phonon modes increase with temperature and transport more heat energy across interface and results in lowering the thermal interfacial resistance at high temperature.;The propagation of heat pulses in zigzag and armchair double wall nanotubes (DWNTs) are also investigated using molecular dynamics simulations. It is found that the leading heat wave packets in zigzag (9,0)/(18,0) and armchair (5,5)/(10,10) DWNT move with the speed of longitudinal acoustic (LA) phonon modes. The intensities of the leading heat wave packets in outer and inner shells in DWNTs were found to be five to seven times larger than that of the corresponding single wall nanotubes (SWNT). The heat energy carried by the leading heat wave packets in zigzag DWNT was about four and five times more than those in armchair DWNT shells. Within the leading LA wavepacket, the strain in the inner shell of the DWNTs is stronger than strain in the outer shell and considerably larger than strain in the corresponding SWNTs. The regions with the largest strain coincide with the regions of high kinetic temperatures within the LA mode wave packets. The higher energy of the LA mode waves in DWNT shells compared to SWNT is attributed to the presence of higher strain fields in DWNT compared to individual SWNT. The higher strain in the inner shell of DWNT compared to the outer shell accounts for the three to five times higher kinetic energy of leading wave packets in inner shells compared to those in outer shells. The induced strain fields in zigzag DWNT are distributed over a wider region compared to armchair DWNT and the strain in inner and outer shells of zigzag DWNT are out phase by 180°.