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Epitaxial La0.7(Pb1−xSrx)0.3MnO3 Thin CMR Film Room Temperature Bolometer
Published online by Cambridge University Press: 10 February 2011
Abstract
Using pulsed laser deposition technique we fabricated films of a continuous series of solid solutions La0.7(Pb1−xSrx)0.3MnO3, which undergo metal-to-insulator phase transition close and above room temperature. The optimal composition for uncooled bolometer applications was found at x = 0.37 with maximum of TCR = 7.4 %K−1@ 295 K. Room temperature bolometer demonstrator has been built and tested. Relatively low excess noise (magnitude γ/n of 3·10−21 cm−3) and high TCR enabled achievement of high signal-to-noise ratio of 8·106 √-Hz/K. The observed frequency dispersion of bolometer response has been ascribed to three relaxation mechanisms of the heat transfer: from film thermistor to substrate, from substrate to thermostat, and heat transfer via leads. For fabricated bolometer heat transfer from substrate to thermostat was found to be the slowest one with a time constant of 0.5 s (correspondent substrate-to-thermostat thermal conductance is G = 3·10−3 W/K). Bolometer performance test yields the responsivity ℜ = 0.6 V/W, detectivity D = 9·106 cm√Hz/W and noise equivalent power NEP of 3·10−8 W/√Hz at 30 Hz frame frequency. Further improvement of bolometer thermal isolation using the micromachining technique is believed to achieve the responsivity about 4·103 V/W and detectivity higher than 109 cm√Hz/W@30 Hz.
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- Copyright © Materials Research Society 2000