Pt-based metallization of PMOS devices for the fabrication of monolithic semiconducting/YBa2Cu3O7-d superconducting devices on silicon

Mo, Pt, Pt/Mo and Pt/Ti thin films have been deposited onto Si and SiO2 substrates by RF sputtering and annealed in the YBa2Cu3O7-d growth conditions. The effect of annealing on the sheet resitance of unpatterned layers was measured. A Pt-based multilayered metallization for the PMOS devices was proposed and tested for the monolithic integration of PMOS devices and YBCO sensors on the same silicon substrate. The best results were obtained with a Pt/Ti/Mo-silicide structure showing (0.472 \Omega_{\Box}) interconnect sheet resistivity and $2 \times 10^{-4} \Omega \cdot cm^{2}$ specific contact resistivity after annealing for (60) minutes at (700^{\circ})C in (0.5) mbar O(_{2}) pressure.Comment: 6 pages, accepted for Microelectronic Engineering, elsevie

YBCO Transition Edge Sensors Used For Very Low Noise Thermal Control

In electrically substituted radiometers, the ultra low noise control of the temperature is required. In this framework, we present results dedicated to the temperature regulation of copper plates, 3 cm diameter and 1 mm thick, using YBa2Cu3O7-d (YBCO) transition edge sensors (TES). One of the TES was used as the active thermometer of the temperature control unit, whereas the two others measured the plate temperature behavior. Two heating resistors were wound along a spiral pattern, just underneath the copper plate, to minimize the heating delay. The correlation between the two TES was clearly highlighted by applying a small heat perturbation through the second distributed resistor, the path of which closely follows that of the main resistor. Calibrated temperature oscillations of 30 microK rms at 10mHz together with spectral analysis were measured and a temperature resolution in the range of a few microK rms was achieved.Comment: 6 pages, ASC 2002 (Applied Superconductivity Conference), Houston, TX USA (Aout 2002): Oral contribution, to be published in IEEE Trans. Appl. Supercond. June 200

Sub-nT resolution of single layer sensor based on the AMR effect in La_2/_3Sr_1/_3MnO_3 Thin Films

Single-layer magnetoresistive sensors were designed in a Wheatstone bridge configuration using La_2/_3Sr_1/_3MnO_3 ferromagnetic oxide thin film. Uniaxial anisotropy was induced by performing epitaxial deposition of the films on top of vicinal SrTiO_3 substrate. X-ray scan confirms the high crystalline quality of the films and the magnetic anisotropy was checked by magneto-optical Kerr effect measurements. Thanks to the anisotropic magnetoresistive effect and the very low noise measured in the devices, sub-nT resolution was achieved above 100 Hz at 310 K

Etude du retournement de l'aimantation par microscopie magnéto-optique Kerr et de la magnétorésistance dans des couches minces de La0.7Sr0.3MnO3 à température ambiante

Nous avons étudié à température ambiante le retournement de l'aimantation par microscopie magnéto-optique Kerr longitudinale de trois couches minces La0,7Sr0,3MnO3 (LSMO) déposées sur des substrats SrTiO3 vicinaux et non vicinaux. Ce matériau ferromagnétique à température ambiante présente un intérêt pour la réalisation des dispositifs magnétorésistifs non refroidis. Avant de concevoir un capteur magnétorésistif, il est indispensable de comprendre le comportement magnétique du matériau qui le constitue. Nous avons observé trois types de retournement de l'aimantation (retournement par nucléation et propagation de parois, retournement cohérent, ou mélange des ces deux types). Nous avons montré l'effet de plusieurs paramètres (orientation du champ magnétique par rapport aux marches et au courant électrique, taille du motif et épaisseur de la couche). Une dépendance temporelle du retournement de l'aimantation a été également remarquée. La magnétorésistance à très faible champ magnétique est influencée par la présence ou l'absence de parois de domaine et par l'orientation du champ par rapport au courant et marches. La mesure des différentes sensibilités magnétiques conduit à une sensibilité de 1000 %/T dans l'échantillon vicinal de petite épaisseur, ce qui est dix fois plus que dans une couche non vicinale, tout en conservant le même niveau de bruit à basse fréquence. Ces résultats ouvrent donc des perspectives intéressantes en termes d'applications.We studied at room temperature the magnetization reversal of three samples patterned in La0.7Sr0.3MnO3 (LSMO) thin films deposited on vicinal and on non vicinal SrTiO3 substrates by longitudinal Kerr microscopy. LSMO is a ferromagnetic material at room temperature and is promising for uncooled magnetoresistive devices. Before designing a magnetoresistive sensor, it is important to understand the magnetic behavior of the material. We observed three types of magnetization reversal (by nucleation and propagation of domain walls, coherent rotation, or a mixture of both types). We have shown the effect of several parameters, such as the magnetic field orientation with respect to the steps and to the current, the device size and the layer thickness. The effect of time on the magnetization reversal was also pointed out. The very low field magnetoresistance at room temperature is strongly influenced by the presence or absence of domain walls and by the magnetic field orientation with respect to the current and steps. The magnetic sensitivities were about 1000 % / T in the vicinal film with small thickness, which is ten times more than in a non vicinal film. In the mean time, no increase of the low frequency noise was observed, which opens interesting perspectives in terms of applications.CAEN-BU Sciences et STAPS (141182103) / SudocSudocFranceF

Propriétés magnétiques, orbitales et de transport d hétérostructures basées sur LaMnO3

Dans la première partie de la thèse nous traitons les propriétés magnétiques, orbitales et de transport des super-réseaux (LaMnO3) 2N (SrMnO3) N et des couches minces de LaxMnO3-d déposées par épitaxie à jet moléculaire (MBE) sur des substrats SrTiO3. Ces super-réseaux représentent un nouveau genre d'hétérostructure, récemment très étudié, composée par un nombre entier de mailles, où des effets de reconstruction électronique aux interfaces sont prévus. Les deux systèmes sont étudiés par des techniques traditionnelles (transport, aimantation par SQUID) et par des techniques d absorption et d'émission de rayon X par rayonnement de synchrotron. Des informations précieuses sur le ferromagnétisme, l'antiferromagnétisme et l ordre orbital sont obtenues. Dans la deuxième partie du travail de thèse, des techniques de lithographie optique et des différentes techniques de dépôt sont utilisées afin d'effectuer des mesures de transport avec courant perpendiculaire à la surface des échantillons (CPP) et sous l'effet de champ électrique. La technique CPP peut donner de l'information supplémentaire sur les interfaces par rapport aux mesures de transport traditionnelles. La possibilité d'application d'une telle technique également aux multicouches multiferroïques est étudiée. L'effet de champ a été largement étudié dans des systèmes de manganite, puisque il représente une méthode pour changer la densité de porteurs, et afin de fabriquer des dispositifs à effet de champ avec des oxydes. On rapporte les résultats de l'optimisation de telles techniques, ainsi que l'optimisation des matériaux utilisés en tant qu électrode de base, isolateur de flanc ou de barrière et électrode supérieure.The first part of the thesis deals with the magnetic, orbital and transport properties of (LaMnO3)2N(SrMnO3)N digital superlattices and of LaxMnO3-d thin films, both deposited by molecular beam epitaxy (MBE) technique on SrTiO3 substrates. The (LaMnO3)2N(SrMnO3)N digital superlattices represent the new kind of heterostructure, actually under intensive study, composed by an integer number of unit cells, where electronic reconstruction effects at the (clean) interface are expected. Both systems where studied by traditional techniques (transport measurements, SQUID magnetometer) and soft X-ray absorption and emission techniques by synchrotron radiation. Collecting the data from different measurement techniques, precious information about ferromagnetism, antiferromagnetism and orbital ordering is obtained. In the second part of the thesis work, optical lithography techniques and different deposition techniques are employed in order to perform transport measurement in current perpendicular to plane (CPP) configuration and field effect measurements. The CPP technique would allow to gain more information respect to the in-plane measurements as the ones used in the first part of the thesis. The possibility of application of such technique also to multiferroic multilayers is also investigated. Field effect has been widely investigated in manganite (especially LMO-based) systems, as it represents a method to tune the carrier density, and in order to engineer all oxide field effect devices. The results of the optimization of such techniques, together with the optimization of the materials needed as base electrode, side and gate insulators and top electrode is reported.CAEN-BU Sciences et STAPS (141182103) / SudocSudocFranceF

Manganites à magnétorésistance colossale pour la réalisation de capteurs

The growth of high quality epitaxial La0.7Sr0.3MnO3 thin films was controlled on various substrates, including SrTiO3 (001), (110), vicinal substrates and Si. The design and development of applications such as uncooled bolometers and spintronic devices could then be considered. In this work, different deposition techniques were used: sputtering, pulsed laser deposition, assisted or not by RHEED (Reflection High Energy Electron Diffraction). The samples were characterized by X-ray diffraction, particularly studying epitaxy and strain in the layers. Further analyzes using RHEED, LEED (Low Energy Electron Diffraction), and STM/AFM (Scanning Tunneling and Atomic Force Microscopies) were also conducted, as well as resistivity and magnetization measurements as a function of the temperature. The effect of the orientation of the SrTiO3 substrate has been demonstrated. Finally, three examples of spintronic devices based on dead layer, vicinal surfaces or spin injection are presented.CAEN-BU Sciences et STAPS (141182103) / SudocSudocFranceF

Mesoscopic electronic heterogeneities in the transport properties of V 2 O 3 thin films

International audienc

Mesoscopic electronic heterogeneities in the transport properties of V 2 O 3 thin films

International audienc