12−μm-Pitch Electromechanical Resonator for Thermal Sensing

We provide here a demonstration of 12−μm-pitch nanoelectromechanical resonant infrared sensors with fully integrated capacitive transduction. A low-temperature fabrication process is used to manufacture torsional resonator arrays. An H-shaped pixel with 9−μm-long nanorods and (250×30)−nm^2 cross section is designed to provide high thermal response whose experimental measurements reach up to 1024  Hz/nW. A mechanical dynamic range of over 113 dB is obtained, which leads to an Allan deviation of σ_A = 3×10^(−7) at room temperature and 50-Hz noise bandwidth (σ_A = 1.5×10^(−7) over 10 Hz). These features allow us to reach a sensitivity of (8–12)−μm radiation of 27  pW/√Hz leading to a noise-equivalent temperature difference (NETD) of 2 K for a 50-Hz noise bandwidth (NETD = 1.5  K at 10 Hz). We demonstrate that the resolution is no more set by the phonon noise but by the anomalous phase noise already encountered in flexural nanoresonators. By both improving the temperature coefficient of frequency of a factor 10 and using a readout electronics at the pixel level, these resonators will lead to a breakthrough for uncooled infrared detectors. We expect that the NETD will rapidly drop to 180 mK with electronics close to the pixel. As a result of the features of our torsional resonators, an alternative readout scheme of pixels is suggested.