Simulation And Experimental Investigation On Microscale Interfacial Heat Transfer

In this dissertation,molecular dynamics simulation and time-domain thermoreflectance(TDTR)measurement combined with theoretical model are implemented to study the heat conduction along the in-plane or the out-of plane direction of the interface which is formed as the nanostructures assembled together.The topics are as follows:The Nonequilibrium molecular dynamics(NEMD)simulation method is used to simulate the in-plane thermal conductivity of single and bi-layer silicon thin films with perfectly smooth and rough interfaces between the constituent single layer films.For single layer films,the surface roughness can greatly enhance the phonon diffusive scattering at the boundary and reduce the thermal conductivity of the films.For bi-layer films,interface roughness can increase the effect of transmission phonon on the in-plane thermal conduction of bilayer films,and as a result,the thermal conductivity of bi-layer films can be higher than that of single layer films.The contact thermal conductances between two carbon naotubes(CNTs)are also studied by using NEMD method.The contact patten,the layer number,the axial stress and the defect effects(vacancy and hydrogenation)on the thermal conductance are investigated.Simulation results show that the former three effects have a great influence on the heat conduction across the interface between CNTs.Especially,the variation of contact patten can lead to the variation of thermal conductance by an order of magnitude.Thickness dependent contact thermal conductance(CTC)between thin films is still investigated using NEMD method.The simulation results show that the CTC between multilayer graphene is thickness dependent while that of silicon thin film is almost thickness independent.In addition,size effect strength is defined to assess the effect of phonon focusing on the thickness dependent CTC in the frame of phonon irradiation based thermal boundary conductance calculation.The anisotropic Debye model is applied to calculate the size effect strength.The results show that the phonon focusing dose play an important role in the thickness dependence of CTC.The thermal conductances across Au/graphene/Au and Au/H-graphene/Au interface are measured through TDTR method.The measurement results show that the thermal conductance decrease by?50%when the graphene is hydrogened.In addition,NEMD method is implemented to analyze the experimental results.The simulation results show that the hydrogenation effect can reduce the the thermal conductance by no more than 30%.The difference between the simulated and experimental results show that other carriers except phonons have a negligible contribution to the thermal conductance across the Au/graphene/Au interface.On this basis,thermal conductances across Au/H-graphene/SiO2 and Au/graphene/SiO2 interfaces are measured by using TDTR method.By analysising the measurement results,we find that the contribution of electrons to the thermal conductance across Au/graphene/Au interface is?50%of the total value.