How to get phonon noise limited uncooled bolometers

In this paper we present the careful study of the noise of uncooled bolometers made of free-standing epitaxial La 0.7 Sr 0.3 MnO 3 /SrTiO 3 (LSMO/STO) thin films fabricated by micromachining of the silicon substrates. Relatively high values of Temperature Coefficient of Resistance, named TCR = 1/R×dR/dT (about 0.02 K −1 ), could be achieved in LSMO at room temperature, and very low values of the thermal conductance (about 10 −7 W·K −1 ) could be measured in the 2 μm wide suspended bridges. The resulting bolometer responsivity could thus be increased by more than 4 orders of magnitude compared to non-suspended bolometers. Thanks to the low thermal conductance and to the low 1/f noise (normalized Hooge parameter in the order of 10 −30 m 3 or even below), we could demonstrate that the phonon noise, also known as thermal fluctuation noise, which can be considered as the limit noise source for bolometers, could be dominant. The uncooled LSMO bolometers finally showed record low Noise Equivalent Power of about 10 −12 W.Hz −1/2 at room temperature.