Low-noise La0.7Sr0.3MnO3 thermometers for uncooled bolometric applications -: art. no. 024903

We report measurements of the temperature coefficient of the resistance (TCR) and the low-frequency noise of epitaxial La0.7Sr0.3MnO3 (LSMO) thin films deposited on SrTiO3 (STO) and (LaAlO3)(0.3)(Sr2AlTaO6)(0.7) substrates. An x-ray-diffraction study showed that the films were (001) oriented. A normalized Hooge parameter of 9x10(-31) m(3) was measured at 300 K in the case of a 10-mu m-wide, 575-mu m-long line patterned in the 200-nm-thick film grown on STO substrate. This value is among the lowest reported values for manganites and close to values measured in standard metals and semiconductors. The corresponding noise equivalent temperature (NET) was constant in the 300-340 K range and equal to 6x10(-7) K Hz(-1/2) at 10 Hz and 150 mu A for a 10-mu m-wide, 575-mu m-long line patterned in a 200-nm-thick LSMO film. This very low NET value is comparable to the best published results for manganites and was even found to be lower than the NET of other uncooled thermometers such as amorphous semiconductors, vanadium oxides, or semiconducting YBa2Cu3O6+sigma. This can easily be explained by the lower noise level of epitaxial manganites thin films compared to others. The results show that despite a TCR of only 0.017 K-1 at 300 K, and thanks to a very low-noise level, LSMO thin films are real potential material for uncooled thermometry and bolometry. (c) 2006 American Institute of Physics.