Near-field Heat Transfer Under Electron Tunneling And External Electric Field

With the development of micro-nano-scale technology,micro-nano-scale thermal phenomena have been studied more and more widely.In actual nanoscale devices,the near-field effect is also strongly valued.When the distance between two black bodies is greater than tens of microns,the radiative heat transfer can be solved by Planck’s law,which is independent of distance.However,when the distance between two objects is smaller than the characteristic wavelength,the heat flux changes drastically with the distance.As the vacuum gap becomes smaller,the amount of heat transfer increases exponentially.This is caused by coupling tunneling of evanescent waves on the surface of the medium.As the heat transfer distance is further reduced,the heat transfer caused by electron transport gradually increases,which is called as the extreme near-field heat transfer.The influence of barriers of different metal materials on heat transfer is given.Based on the non-equilibrium Green’s function method,this work calculates the extreme near-field heat transfer between metals due to the Coulomb fluctuation effect firstly.The influence of parameters such as chemical potential and temperature difference on heat transfer is analyzed.The effect of potential barrier on heat transfer between different metal materials is analyzed.The influence of different metal material’s potential barrier on heat transfer is given.Using the electron tunneling model,the ultra-close heat transfer caused by the tunneling effect of electrons in the vacuum junction is calculated.As the distance increases,the barrier height increases rapidly,and the heat flux is already weak at a distance of 0.5 nm.In this work,based on fluctuational electrodynamics,the near-field radiation heat transfer between the metal plates is studied.By applying a direct current potential difference between the metal plates,considering the coupling effect of the wave displacement of the plate surface and the surface charge,the reflection coefficient of the polarized wave between the charged metal plates is rectified.This work calculates the influence of the external electric field on the near-field radiation heat transfer between the three metal materials of gold,silver and copper.The results show that at the same distance,the electric field of the same intensity has an obvious enhancement effect on the near-field radiation heat flux between the copper plates.It is found that for metal materials with high mechanical polarization,as the electric field intensity increases,the heat flux first increases and then decreases.This work gives the corresponding electric field intensity at the peak of the radiative heat flux between the copper plates under different spacing.The relationship between the distance and electric field intensity is expressed asE_p(?)exp(7)0.0356d(8).Finally,this work proposes an interparticle thermal radiative diode based on non-reciprocal surface plasmons.By applying an electric field on both sides of the graphene grating,a drift current can be generated in the graphene strips,which causes the non-reciprocity of the surface mode.The grating is placed on one side of the two nanoparticles,which builds an additional channel for heat transfer between particles.By changing the distance between the grating and the particles and the angle of the grating,the heat flux between the particles can be adjusted actively.In addition,I also analyzed the effect of the filling rate of the grating and the chemical potential of graphene on the rectification effect of the system.The chemical potentials corresponding to the peak rectification coefficients under different grating filling ratios are given in this work.When the grating filling rate is 0.5,the chemical potential corresponding to the maximum rectification coefficient is 0.32 e V.The rectification coefficient of the diode composed of the graphene grating system is 78.84,while the rectification coefficient of the single-layer graphene system is only 0.17.In addition,the direction of the diode proposed in this work does not change with the particle height and the chemical potential.It is found that when the angle between the strip and the particle is 8.5°,the rectification of the system is the highest.Compared with the single-layer graphene system,the grating system has a higher rectification coefficient and stronger directional stability under a large chemical potential.