Near-field radiative heat transfer between thin MgF$_2$ dielectric film on SiO$_2$

Abstract

Once a body reaches a temperature greater than absolute zero, electromagnetic wave emissions are inevitable because of the increase in temperature. Radiative heat transfer has been broken down into two primary categories up to this point. These categories are based on the sample’s geometric dimension and the characteristic wavelength established by Wien’s displacement equation. The term ”far-field radiative heat transfer” refers to a kind of radiative heat transfer that occurs when the predominant wavelength is much shorter than the distance that separates the emitter and the receiver (FFRHT). In contrast, ”near-field radiative heat transfer” refers to the process of radiative heat transfer that occurs when the distance between the objects is comparable to or less significant than the wavelength of the radiation (NFRHT). The Stefan–Boltzmann rule dictates that the NFRHT between two substances separated by a nanoscale vacuum gap must be greater than the black-body limit. The preponderance of evanescent waves or photon tunneling is to blame for this observation. The enhancement of the NFRHT was facilitated by the surface waves, which included surface phonon polaritons (SPhPs) and surface plasmon polaritons (SPPs), respectively. The introduction of coupling materials has the potential to trigger these waves. Because they can sustain SPhPs even at room temperature, dielectrics are ideal. This article discusses the current developments that have been made regarding materials that enable SPhPs and SPPs surface modes and boost radiative heat transfer. In this study, we developed a unique experimental setup to strictly control the XYZ and tilt motions of the sample while also maintaining the nano-gap spacing and parallelism of the arrangement. After that, we investigated the radiative heat flow between two parallel, MgF$_2$-dielectric-coated SiO$_2$ plates. With our measurements’ help, we could determine a distance of 700-nm. The experimental result for heat flow is comparable to the theoretical one, and enhanced heat flux is observed compared to the bulk SiO$_2$ silicon plates.