Near-Field Thermal Radiation across Solid-State Gaps

Near-field thermal radiation has attracted great interest due to heat transfer exceeding blackbody radiation by several orders at nanoscale separation gaps. Although extensive research is devoted for understanding of physics, feasibility of near-field based thermal devices with large scales is extremely low owing to the difficulty in controling and sustaining the corresponding separations between heat exchanging materials in macroscales. In this study, we explore near-field radiation through solid-state gaps sandwiched between heat exchanging materials with large lateral dimensions. Our theoretical design employs solid-state thin films as a separating medium. We derive a multimode, nanoscale heat transfer model by incorporating Boltzmann’s equation to fluctuational electrodynamics, and compare energy transport capacity of thermal radiation and conduction across the thin film and interfaces at both sides of the film. Our systematic approach enables defining key dimensions and parameters that govern radiation and conduction heat transfer through the solid-state gap. Using quasi steady-state approximation, this study also investigates and compares heat transfer dynamics of radiation and conduction across the film and the interfaces of the film in time domain. This study will shed light on the feasibility of solid-state based near-field thermal radiation and has potential to open a new avenue for possible application of near-field enhancement using macroscale devices.