This work opens the way to a new uncooled microbolometers based on the variation of the electrical resistance with temperature around 300 K in La0.7Sr0.3MnO3 thin films on buffered silicon substrates. Thermal conductance has been reduced thanks to silicon micromachining techniques. We verified that the electrical properties (electrical resistivity and low frequency noise) of La0.7Sr0.3MnO3 are not degraded on the suspended micro-bridges (width of 2 or 4 µm and length of 50 to 200 µm). The measured thermal conductance is well described by a simple analytical model. The thermal insulation of the detectors is reduced by 5 orders of magnitude, thus increasing the microbolometers sensitivity. The estimated specific detectivity in the bandwidth is equal to 1.1 × 1010 cm.Hz-1/2.W-1 at 1.5 µm and 300 K, which is very close to the theoretical limit for uncooled thermal detectors (1.8 × 1010 cm.Hz-1/2.W-1). Our phonon noise-limited radiation detectors exhibit a low effective time constant (<1 ms). They could find applications where a small number of detectors with a high specific detectivity (or a small time constant) are required. This is in the case of infrared spectrometry or non-dispersive infrared gas detectors for examples. Coupled to antennas, our bolometers could also be usefull in THz detection.
