Experimental study of near-field radiative heat transfer between large-area polar dielectric films

Utilizing polar dielectric films can improve the performance of near-field thermophotovoltaic system. To confirm the enhancement of near-field radiative heat transfer (NFRHT) achieved by large-area polar dielectric films, we built an experimental setup and observe NFRHT between two 250 nm-thick SiO₂ films on intrinsic Si substrate with an area 5 × 5 mm². The two films are supported by SiO₂ nano-spacers with a height of 302 nm. Temperature difference between the two films varies from 13 K to 42 K at room temperature. The observed near-field radiative heat flux closely matches the theoretical values, which surpasses substrate-only system by up to 9.87 times and could reach up to 7.45 times that of blackbody radiation due to excitation of the surface photon polaritons modes. These results demonstrate the effectiveness of polar dielectric films in enhancing NFRHT.