Giant Enhancement in Radiative Heat Transfer in Sub-30 nm Gaps of Plane Parallel Surfaces

Radiative heat transfer rates that exceed the blackbody limit by several orders of magnitude are expected when the gap size between plane parallel surfaces is reduced to the nanoscale. To date, experiments have only realized enhancements of similar to 100 fold as the smallest gap sizes in radiative heat transfer studies have been limited to similar to 50 nm by device curvature and particle contamination. Here, we report a 1,200-fold enhancement with respect to the far-field value in the radiative heat flux between parallel planar silica surfaces separated by gaps as small as similar to 25 nm. Achieving such small gap sizes and the resultant dramatic enhancement in near-field energy flux is critical to achieve a number of novel near-field based nanoscale energy conversion systems that have been theoretically predicted but remain experimentally unverified.