Extended Data Fig. 4: Quantification of parasitic energy transfer mechanisms.
From: Hundred-fold enhancement in far-field radiative heat transfer over the blackbody limit
a, Measured Grad,eff between 2-μm-thick SiN membranes at various temperatures and pressures. Measurements performed at 10−3 torr (black squares) and 10−6 torr (red diamonds) give virtually identical results, strongly supporting the expectation that conduction via remaining gas molecules plays no role. b, Measured Grad,eff between 270-nm-thick SiN membranes at various temperatures. The inset illustrates how thermal energy between the devices can potentially couple via conduction through the substrate. The plotted data correspond to two device geometries: devices with 400-μm-long support beams (black squares) and devices with 150-μm-long support beams (red squares). Because devices with short and long beams have identical Grad,eff, it is clear that coupling via the suspending beams is negligibly small. c, Schematic describing the control experiment, where an emitter and a receiver are separated by a gap of about 1 mm and an Al foil is placed between them, blocking direct RHT (not drawn to scale and proportion). d, Measured coupling signal between 2-μm-thick emitter and receiver membranes across a 1-mm-wide gap (T = 300 K). Signals without (black squares) and with (red circles) an Al foil in the gap are shown. The inset (cross-sectional view of the devices) illustrates how the Al foil shield blocks direct RHT between the membranes but potentially allows RHT via specular reflections. Because the signal obtained in the presence of the Al blocker represents the noise floor of our measurement, we conclude that there is negligible heat transfer (via RHT or otherwise) in the presence of the Al foil. This control experiment provides unequivocal evidence that energy transfer between the membranes is mediated exclusively by direct radiation. e, Scanning electron microscope image of two emitter and receiver pairs suspended in separate through-holes on the same handle substrate. f, Measured coupling signal between 486-nm-thick devices (T = 100 K). Signals from adjacent emitter and receiver devices (that is, in the same through-hole; see pair 1 in e) with a 20-μm-gap (black squares) are compared with the signals measured when the emitter and receiver devices are suspended in separate through-holes on the same silicon handle substrate (red circles).
