Low-frequency noise considerations for sensors based on manganites

International audienceLow frequency noise considerations for sensors based on La0.33Sr0.67MnO3 (LSMO) thin films are discussed in this paper. Thanks to special attention on the film quality, onthe electrical readout electronics and on the patterned geometries, epitaxially grown LSMO thin films can show a very low level of low-frequency noise and can thus be used to fabricate high signal-to-noise ratio sensors such as uncooled bolometers and uncooled low-field magnetoresistances

La0.7Sr0.3MnO3 suspended microbridges for uncooled bolometers made using reactive ion etching of the silicon substrates

International audienceSuspended La0.7Sr0.3MnO3 (LSMO) microbridges were fabricated using standard silicon micromachining techniques. First epitaxial LSMO thin films were deposited on SrTiO3 (STO) buffered Si (001) substrates by molecular-beam epitaxy. A simple two photolithography step process using the reactive ion etching of the silicon substrate to release the suspended microbridges was developed. The electrical resistivity as a function of temperature of 4 lm wide 50-200 lm long and 75 nm thick LSMO/STO fully processed suspended microbridges was very close to the characteristics of the initial LSMO thin films, demonstrating that the fabrication process did not degrade the quality of the LSMO. The thermal conductance of the processed bolometers was very low (of the order of 10 7WK 1) at 300 K. These structures are promising for uncooled bolometer applications and other micro-electromechanical systems based on LSMO or other epitaxial functional oxides

Bolomètres non refroidis à base de couche minces La0,7Sr0,3MnO3 : modèle thermique, caractérisations électrique et optique

The aim of this thesis is to evaluate LSMO (La0,7Sr0,3MnO3) thin films deposited on substrate as room temperature radiation detector, by using the variation of its resistance electric near 300 K. An optical measurement setup has been designed and realized to achieve this objective. This setup was to characterize the LSMO samples as bolometrical radiation detector. A detailed thermal model of thin-film-on-substrate structure is proposed. It interprets the variation of the optical responsivity versus the modulation frequency of laser radiation power. The discussion of this model includes presenting the heat diffusion into substrate, and the film-substrate interface thermal resistance. This model has been analyzed and validated using the measurement results of many detection surfaces (meander shape) and substrate materials. The value of film-substrate interface thermal resistance was estimated for different substrates. The bolometer characterization includes the thermal and electrical parameters, like TCR and thermal conductance, needed to qualify its performance. Also, measurement and analysis of optical responsivity and noise for many different pixel surfaces on different substrates is presented. The role of detector geometry (pixel surface, film thickness, and number of strips) and substrate material (SrTiO3, MgO, SrTiO3/Si) on the bolometer performance is studied by using the measurement results and calculation data issued from the proposed model. The measured specific detectivity increases for higher pixel size and lower substrate material thermal conductivity. We estimated 2x107 cm.W-1.Hz1/2 for 200x200 µm² LSMO/STO sample. For LSMO/Si, estimation of 21 µs response time was achieved for 50x50 µm², which is comparable to that of photon detectors.Ce travail évalue la potentialité de couches minces LSMO (La0,7Sr0,3MnO3) déposées sur substrat comme détecteur de rayonnement à température ambiante, en exploitant la variation de sa résistance électrique au voisinage de 300 K. Un banc de mesure optique a été mise en place (conception et réalisation) pour achever cet objectif. Ce banc a été utilisé pour caractériser les échantillons LSMO comme détecteur de rayonnement bolométrique. Un modèle thermique analytique détaillé de la structure couche-mince-sur-substrat est proposé. Il interprète les variations de la sensibilité optique par rapport la fréquence de modulation de la puissance laser rayonnée. La discussion du modèle comprend la présentation de la diffusion de la chaleur dans le substrat et la résistance thermique d'interface couche-substrat. Ce modèle a été analysé et validé à l'aide des résultats de mesure de plusieurs surfaces de détection (méandre forme) pour différents matériaux de substrat. La valeur de la résistance thermique de l'interface couche-substrat a été estimée pour les différents substrats. La caractérisation de bolomètre inclut les paramètres thermiques et électriques, comme le TCR et la conductance thermique, nécessaires pour qualifier sa performance. Ainsi, la mesure et l'analyse de sensibilité optique et le bruit de plusieurs pixels surfaces sur différents substrats sont présentés. Le rôle de pixel géométrie (pixel surface, l'épaisseur du film, nombre de méandres) et le matériau de substrat (SrTiO3, MgO, SrTiO3/Si) sur les performances du bolomètre est étudiée, en utilisant les résultats de mesure et les données de calcul issus du modèle. La détectivité spécifique mesurée augmente pour une taille du pixel plus grand et une conductivité thermique du substrat plus petit. On estime 2x107 cm.W-1.Hz1/2 pour échantillon 200x200 µm² LSMO/STO. Pour LSMO/Si, un temps de réponse 21 µs été obtenue pour 50x50 µm², ce qui est comparable à celui des détecteurs photonique

Analysis of operating temperature and bias current as linked parameters for the optimization of uncooled suspended La0.7Sr0.3MnO3 bolometers on silicon substrates

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Measurement of thermal conductance of La0.7Sr0.3MnO3 thin films deposited on SrTiO3 and MgO substrates

International audienceWe present measurements of the thermal conductance of thin-film-on-substrate structures that could serve as thin film uncooled bolometers. Studied samples were 75 nm thick epitaxial La 0.7 Sr 0.3 MnO 3 thin films deposited on SrTiO 3 (0 0 1) and MgO (0 0 1) substrates patterned in square geometries of areas ranging from 50 µm × 50 µm to 200 µm × 200 µm. The model allows estimating thermal boundary con-ductance values at the interface between film and substrate of 0.28 ± 0.08 × 10 6 W K −1 m −2 for LSMO/STO (0 0 1) and 5.8 ± 3.0 × 10 6 W K −1 m −2 for LSMO/MgO (0 0 1) from measurements performed in the static regime. Analytical expressions of thermal conductance and thermal capacitance versus modulation fre-quency are compared to measurements of the elevation temperature due to absorbed incoming optical power. The overall good agreement found between measurements and model finally provides the pos-sibility to calculate the bolometric response of thin film bolometers, thus predicting their frequency response for various geometries

Bolomètres non refroidis à base d'oxyde de manganèse

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Bolomètres non refroidis à base d'oxyde de manganèse

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Uncooled phonon noise limited La0.7Sr0.3MnO3 suspended bolometers

International audienceLa0.7Sr0.3Mn03 (LSMO) suspended bolometers of various geometries have been fabricated using silicon micromachining techniques. Thanks to adequate geometry design and to the operating conditions (temperature and bias current), these uncooled bolometers could be limited by phonon noise and achieve NEP values below 1 pW Hz-1/2 around 300 K

Intégration des oxydes fonctionnels sur silicium : le cas des bolomètres à base de couches minces La0.7Sr0.3MnO3

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Uncooled La0.7Sr0.3MnO3 suspended bolometers at optimal operating conditions

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