Uncooled bolometer response of a low noise La2/3Sr1/3MnO3 thin film

We report measurements of the optical responses of a La2/3Sr1/3MnO3 (LSMO) sample at a wavelength of 533 nm in the 300-400 K range. The 200 nm thick film was grown by pulsed laser deposition on (100) SrTiO3 substrate and showed remarkably low noise. At 335 K the temperature coefficient of the resistance of a 100 micrometers wide 300 micrometers long LSMO line was 0.017 K-1 and the normalized Hooge parameter was 9 e-30 m3, which is among the lowest reported values. We then measured an optical sensitivity at I = 5 mA of 10.4 V.W-1 and corresponding noise equivalent power (NEP) values of 8.1 e-10 W.Hz-1/2 and 3.3 e-10 W. Hz-1/2 at 30 Hz and above 1kHz, respectively. Simple considerations on bias current conditions and thermal conductance G are finally given for further sensitivity improvements using LSMO films. The performances were indeed demonstrated on bulk substrates with G of 10-3 W.K-1. One could expect a NEP reduction by three orders of magnitude if a membrane-type geometry was used, which makes this LSMO device competitive against commercially available uncooled bolometers.Comment: 15 pages. Accepted for publication in Appl. Phys. Let

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

Influence of fabrication steps on optical and electrical properties of InN thin films

This paper reports on a case study of the impact of fabrication steps on InN material properties. We discuss the influence of annealing time and sequence of device processing steps. Photoluminescence (PL), surface morphology and electrical transport (electrical resistivity and low frequency noise) properties have been studied as responses to the adopted fabrication steps. Surface morphology has a strong correlation with annealing times, while sequences of fabrication steps do not appear to be influential. In contrast, the optical and electrical properties demonstrate correlation with both etching and thermal annealing. For all the studied samples PL peaks were in the vicinity of 0.7 eV, but the intensity and full width at half maximum (FWHM) demonstrate a dependence on the technological steps followed. Sheet resistance and electrical resistivity seem to be lower in the case of high defect introduction due to both etching and thermal treatments. The same effect is revealed through 1/f noise level measurements. A reduction of electrical resistivity is connected to an increase in 1/f noise level

Evidence of charge carrier number fluctuations in InN thin films?

Due to its small band-gap and its high mobility, InN is a promising material for a large number of key applications like band-gap engineering for high efficiency solar cells, light emitting diodes, and high speed devices. Unfortunately, it has been reported that this material exhibits strong surface charge accumulation which may depend on the type of surface. Current investigations are conducted in order to explain the mechanisms which govern such a behavior and to look for ways of avoiding it and/or finding applications that may use such an effect. In this framework, low frequency noise measurements have been performed at different temperatures on patterned MBE grown InN layers. The evolution of the 1/f noise level with temperature in the 77 K-300 K range is consistent with carrier number fluctuations thus indicating surface mechanisms: the surface charge accumulation is confirmed by the noise measurements

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

Bruit basse fréquence dans des couches minces La0,7Sr0,3MnO3 gravées (vers la réalisation de micro-capteurs performants)

De nombreux résultats bibliographiques indiquent que le film mince de manganite La0,7Sr0,3MnO3 (LSMO) a de fortes potentialités en tant que capteur bolométrique ou magnétorésistif à température ambiante. De plus, le dépôt de ces couches sur silicium est maintenant technologiquement maitrisé rendant ce matériau compatible avec l industrie de la microélectronique. Les couches étudiées sont déposées sur différents substrats par les techniques d ablation laser pulsée ou d épitaxie par jet moléculaire. La mise en forme des motifs avec différentes géométries a été effectuée par photolithographie et gravure ionique. Cette thèse s intéresse au bruit basse fréquence intrinsèque de ce matériau fixant les performances ultimes du capteur notamment en termes de rapport signal sur bruit. Les études ont été réalisées sur des couches minces gravées en utilisant différentes géométries et différents types de substrat. Les composants se comportent comme des résistances électriques et ont été caractérisés électriquement dans une configuration de mesure en quatre points. Une source de courant optimisée en termes d impédance de sortie et de bruit a ainsi été développée. Il est montré que le bruit intrinsèque de la couche peut être masqué par des contributions de contacts. Des solutions instrumentales et une géométrie optimale des composants sont proposées pour la réalisation d un capteur sans l influence des contacts. Il est de plus montré que le dépôt de ces couches sur silicium avec couches tampons ne dégrade pas les performances en bruit des couches. Enfin les performances d un capteur thermique et magnétique ont été estimées.Numerous bibliographic results show that La0,7Sr0,3MnO3 (LSMO) thin films are potential candidates for ultimate room temperature bolometer or magnetoresistances sensors. Moreover, thin film deposition on silicon is now well controlled leading to the possible integration of this material in classical microelectronic industry. The thin films are deposited on different substrates using pulsed laser deposition or molecular beam epitaxy. The studied devices were etched with different geometries using photolithography and ion etching. This thesis work focuses on LSMO intrinsic low frequency noise that limits the ultimate signal to noise ratio of the sensors. The studies have been performed on different geometries and substrates. Devices are electrical resistances and have been characterized in a four probe configuration: a DC current source with a high output impedance and low output noise has thus been developed. It is shown that the intrinsic noise can be lower than contact contributions. Instrumental solutions and optimal geometries have been proposed to reject the contact contributions. It is also shown that the use of a buffered silicon substrate does not degrade the noise performances. Finally, the performances of bolometric and magnetic sensors have been estimated.CAEN-BU Sciences et STAPS (141182103) / SudocSudocFranceF

CAPTIL, l'empire des sens numériques

International audienc

Proceedings of 22nd International Conference on Noise and Fluctuations (ICNF)

International audienc