Molecular Dynamics Simulations Of Interfacial Thermal Transport In Low-dimensional Carbon Materials

With the progress in fabrication technology,the characteristic length of electronics is usually at nanoscale.The interfacial thermal resistance due to the integration of nanostructures is becoming a hot research topic in thermal management and thermal design with the miniaturization of devices.Recently,low-dimensional carbon materials,especially carbon nanotube and graphene,have widely potential applications in electronics owing to their fascinating electrical and thermal properties.Therefore,the thesis investigated the interfacial thermal transport in low-dimensional carbon materials using classical molecular dynamics simulations.For the structure of vertical carbon nanotubes and silicon substrate,the results show that the interfacial thermal conductance increases with the increase of temperature and length of carbon nanotube.Reducing the strength of covalent bonds in carbon nanotube,increasing the layer and embedded length of carbon nanotube could enhance the matching level of interfacial phonon spectra and the number of interfacial covalent bonds,thus improve the efficiency of interfacial heat transfer.However,the interfacial thermal conductance decreases with the increase of the concentration and the layers of doping atoms near the interface of substrate.For the structure of a horizontal carbon nanotube and graphene nanoribbons,the results show that the interfacial thermal conductance increases monotonically with the temperature and the interfacial van der Waals interaction strength,and the interfacial thermal conductance is about one order of magnitude higher than that without molecular linkers after incorporating molecular linkers into the interface.The interfacial thermal conductance decreases with increasing stretching strain for the model without molecular linkers,while the reduction can be prevented with additional molecular linkers.Further analysis of phonon spectra indicates that larger overlap between the phonon spectra of molecular linkers and sp~3 hybridized C atoms in graphene can compensate for the mismatch of phonon spectra due to the softening of high-frequency phonon modes of sp~2 hybridized C atoms induced by tensile strain.The thesis investigated the thermal rectification in hybrid pristine and silicon-functionalized graphene nanoribbons.The results show that the heat flux is larger from the functionalized section to the pristine section than that in the opposite direction.It was found that thermal rectification can be tuned through the Si/C ratio and silicon distribution.A moderate Si/C ratio and patterned arrangement are preferable to obtain a higher rectification factor.The rectification factor is also sensitive to the temperature difference and the mean temperature.As the length of the system increases,the rectification factor decreases gradually due to the transition from ballistic transport to diffusive transport.By phonon density of states analysis,the thesis found that the difference in the overlap of the phonon spectra for the two heat flow directions is the origin of the thermal rectification phenomena.