Microfabricated Membranes for Radiative Near Field Measurements

We present in this paper measurements of near-field heat transfer across sub-micron gaps between suspended membranes and their substrate. A microfabrication process using amorphous silicon as a sacrificial layer is developed to create membranes (50 μm × 50 μm) with nanoscale separation distance (down to 250 nm). In this configuration, evanescent near-field radiation couples between the membrane and the substrate, which is expected to enhance the heat transfer. Experimental measurements using an embedded heater and thermistor on the membrane demonstrate the enhancement of heat transfer at the smaller gaps, reaching radiation levels beyond the ideal black body. This is the first demonstration of near field heat transfer over large areas in a fully microfabricated device including a gap effect study.