Research On Near-field Thermal Radiation Of HBN And VO₂ Thin Films Structure Based On Graphene Plasmons

Radiative heat transfer is one of the basic ways of heat transfer.the propagation wave behaves the main propagation path of thermal radiation in the far field,while the heat transfer rate is limited by the black body limit(Planck's law).However,evanescent wave plays a major role in the near field.When the distance between two radiative heat exchange objects is comparable to the characteristic wavelength of thermal radiation,the near-field thermal radiation between them is no longer restricted by the blackbody limit,and Planck's law cannot describe the thermal radiation situation.Furthermore,Surface Plasmon Polaritons(SPPs),Surface Phonon Polaritons(SPh Ps)and photon tunneling effect of the radiator will significantly enhance the heat transfer,resulting in an order of magnitude increase in near-field thermal radiation.Therefore,it is particularly important to investigate near-field thermal radiation.Graphene is currently the thinnest and strongest nanomaterial in the world and is dubbed"black gold"by materials scientists.Since the graphene is separated through tape method by scientists,the separation of graphene method as well as the related research on the application of the graphene develops rapidly.Because of its good mechanical properties,electronic effect,thermal properties,photoelectric performance,and other chemical properties,graphene in the near field plays an important role in the research field of thermal radiation.In recent years,structures based on h BN materials have also been widely used in the study of near-field radiation heat flow,while systematic studies on monolayer film structures and complex heterostructures based on VO₂films are relatively few.As a result,this article reports quantitative and qualitative analysis of thermal radiation in h BN film and VO₂ thin film covered by graphene through theoretical calculation based on the fluctuation dissipation theory and electrodynamics fluctuation as well as the theoretical basis of dyadic green's function.this paper studies the h BN film and VO₂ thin film based on graphene complex heterogeneous structure in different vacuum spacing,film thickness,graphene chemical potential of the near field radiation characteristics.The main contents of this paper are as follows:1.The research status of near field radiation of h BN and VO₂ materials is systematically introduced.According to the fluctuation dissipation theory and the basic concepts of fluctuation electrodynamics,effective medium theory and dielectric function model,the theoretical formulas used in calculating the heat flow of near field radiation in this paper are deduced.2.The surface ionization and conductivity of graphene are systematically introduced,and the dielectric functions of h BN,VO₂,Si C,Si and Si O₂ are investigated.The fundamental factors affecting the near-field radiative heat transfer between different materials in the study are expounded.3.The flat structure composed of graphene and h BN thin films and VO₂ thin films is studied,and the h BN-0 and G-h BN-0,V-0 and G-V-0 structures are proposed respectively.Furthermore,the near-field radiation heat flux of G-h BN-0 and G-V-0 structures are calculated when the vacuum spacing,the thickness of the films and the graphene chemical potential changed.It is found that graphene contributed greatly to the enhancement of the near-field radiation heat flux of the films.4.The near-field thermal radiation between the complex flat structures of graphene based h BN films and VO₂ films is studied,and three structures,G-h BN-Si,G-h BN-Si C and G-V-Si O₂ is proposed.The variations of near-field radiation heat flux of the three complex heteroplate structures under the changes of vacuum spacing,film thickness and graphene chemical potential were investigated respectively,and the optimal parameters and structures for enhancing near-field radiation transfer is analyzed through comparison.