Simulation And Experimental Investigation On Turning The Microscale Heat Transfer

Nowadays,With the development of electronic component in nanoscale,the energy density is continually increased,accompanying with a serious problem related to heat dissipation.Therefore,the problem of heat dissipation is becoming increasingly serious.It has become a hot research topic to explore the heat transfer properties of materials in this scale and seek the active control method.In this paper,we have researched the heat conduction of different materials through experimental methods,and studied how to actively control the heat conduction of black phosphorus nanoribbons by molecular dynamics simulation.The results can provide a theoretical reference for the achievement of achieving more efficient heat control and management.The femtosecond laser transient thermoreflectance system was built to obtain the thermal parameters.In this technique,the pulse laser emitted by a femtosecond laser is used to study the heat transfer between different materials.The pulse from laser is split into two beams:The intense beam is focused on the surface of samples after being modulated;The weaker beam can be used to probe the change of optic properties after passing through the delay displacement table.The temperature of surface of sample is related to the thermal properties of substrate and interfacial thermal conductance and some thermal parameters can be obtained by thermal model.In order to study the effect of material modulation on heat conduction.Three groups of samples are prepared,including Al/SiO₂?Au/SiO₂ and Al/GaN,to investigate the heat conduction in the two cases of the same substrate with different films and the same thin films with different substrates.The DMM model is used to connect interfacial thermal conductance,the transmittance of phonon with the ratio of thermal diffusivity to explain the activity of the phonon at the interface.The greater the interfacial thermal conductance,the higher the thermal diffusivity ratio is.Meanwhile,the ratio of the phonon velocity to the velocity of the basal phonon would decrease.The intervention of gallium nitride reduces the ratio of the phonon velocity on interfacial sides,and only a portion of the phonon in the metal interface reaches the substrate,thus reducing the interfacial thermal conductivity.In order to study the effect of interface modulation on heat conduction,graphene is added to the interface to explore the conduction of heat.The results show that interfacial thermal conductivity decreases by half after the modulation of graphene,which is mainly due to the increase of phonon scattering by the intervention of graphene.By applying tensile strain to the black phosphorus nanoribbons,the heat conduction is regulated actively.Whether it is in the armchair direction or in the zigzag direction,the thermal conductivity of the black phosphorus nanoribbons will increase after stretching.Furthermore,in comparison with the zigzag direction,the change rate of the thermal conductivity in the armchair direction is larger.For the same strain,the growth rate of the thermal conductivity in the armchair direction is obviously larger than that in the zigzag direction.The tensile strain can lead to the change of the density of the phonon state and the mean free path,thus causing the change of the thermal conductivity.