Microscope image (top) and spatial scan (bottom) of the spectrally integrated mid-infrared signal ( P MIR , integrated over the detectors spectral bandwidth, lambda = 6–14 m) emitted by the TR2 device under bias. The dashed white box indicates the orientation of the devices graphene channel (black box in the top micrograph) in the image. The bright emission spot, between the source and drain electrodes (left and right gold pads in the top micrograph), indicates that the signal is most intense in that region, revealing that the emission originates from beneath the device channel. By contrast, the devices gold electrodes appear dark because of their low emissivity. Scale bars, 30 m (top) and 20 m (bottom).
