Experimental And Theoretical Reconstruction Of Thermal Boundary Resistance In Nano Film Structures

Micro and nanoscale nanofilm structures are widely used in microscale devices and thermal measurement systems.The thermal transport process is dominated by thermal boundary resistance?TBR?at interfaces in multilayer nanofilm structures.Thermal transport across solid-solid interfaces remains one of the most challenging problems.The predictions by acoustic and diffuse mismatch models rarely agree with experimental data.It is utmost important to experimetally and theoretically characterize the TBR for the deep understanding of thermal transport.Experimentally,for the measurement setup,the traditional 3?system at low and medium frequency is redesigned and extended to wideband to measure TBR at interfaces of nanofilms.With the defrequency technique and noise reduction measures,the moduls including the signal generation,lock-in and apmlification are intergrated.The measurement system is extended to MHz range.Based on 3?technique,the measurement principle is developed for TBR at the interface of nanofilm in different frequency domain.Three unique patterns are used to determine TBR across interfaces in four nanofilm multilayer structures from room temperature to 500 K.In low frequency domain,the TBRs at interface of antireflective film and wide-band semiconductor film are measured respectively by frequency-current sweeping3?method for SiO₂/ZrO₂/Nd:YAG and SiO₂/GaN/Al₂O₃ multilayer nanofilm structures with a reference sample and one metal heater/sensor;the TBR gives no scale effect when the thickness of film is larger than 100 nm.In medium frequency domain,with multiple metal heaters/sensors,the measured TBR and anisotropic ratio of ultrathin HfO₂ films?2-60 nm?both exhibt a decrease trend with increasing thickness.In wide frequency domain,the data from low and high frequency are used to determine the TBR between DLC/CNT array and intrinsic thermal conductivity of DLC film;the temperature-dependent phonon conduction is validated by the trend of temperature dependence of TBR and thermal conductivity.In conclusion,the multiple samples and heaters are incorporated to measure TBR in nanofilm structures when extended to high frequency.Theoretically,the boundary thermal transport is investigated by phonon dynamics for CNT and GaN films.Four phonon thermal models are used to predict the phonon transmissive coefficient and thermal conductance.The phonon inelastic scattering model corrected with the surface roughness effect is used to characterize the temperature depedence of TBR at interfaces for CNT and GaN films.To some degree,the predicted trend of temperature depedence of TBR agrees with the measured result while the magnitude of the discrepancy between the measurement and prediction is about 2-3 orders.The boundary thermal transport is dominated by the nature of phonon dynamics and phonon inelastic scattering process in the nanoscale near-interface region at high temperature.