Growth and characterization of CoO ultra thin films

In this report we present the growth process of the cobalt oxide system using reactive electron beam deposition. In that technique, a target of metallic cobalt is evaporated and its atoms are in-flight oxidized in an oxygen rich reactive atmosphere before reaching the surface of the substrate. With a trial and error procedure the deposition parameters have been optimized to obtain the correct stoichiometry and crystalline phase. The evaporation conditions to achieve the correct cobalt oxide salt rock structure, when evaporating over amorphous silicon nitride, are: 525 K of substrate temperature, 2.5·10-4 mbar of oxygen partial pressure and 1 Å/s of evaporation rate. Once the parameters were optimized a set of ultra thin film ranging from samples of 1 nm of nominal thickness to 20nm thick and bulk samples were grown. With the aim to characterize the samples and study their microstructure and morphology, X-ray diffraction, transmission electron microscopy, electron diffraction, energy dispersive X-ray spectroscopy and quasi-adiabatic nanocalorimetry techniques are utilised. The final results show a size dependent effect of the antiferromagnetic transition. Its Néel temperature becomes depressed as the size of the grains forming the layer decreases.

Le «corps» du texte néotestamentaire dans les films Ben-Hur (1925) et Golgotha (1935)

L'article se propose de discuter la question des modalités de la référence aux évangiles au cinéma en s'attachant à l'étude de la composante verbale et de ses liens avec la représentation de la figure christique dans deux films: le premier, Ben-Hur (Fred Niblo, 1925), est une superproduction produite par Hollywood à l'époque de l'apogée du muet; le second, Golgotha (1935), est réalisé par le cinéaste français Julien Duvivier durant les premières années de la généralisation du parlant. D'un côté l'écrit (sous forme d'intertitres), de l'autre la profération orale d'un texte. Le rapprochement proposé entre ces deux films tient à la façon dont la citation néotestamentaire participe à la construction par le film de la figure de Jésus, ou plutôt à la mise à distance de celle-ci, constamment rejetée dans une forme de hors-champ.

Neuroticism modifies psychophysiological responses to fearful films

Background: Neuroticism is a personality component frequently found in anxious and depressive psychiatric disorders. The influence of neuroticism on negative emotions could be due to its action on stimuli related to fear and sadness, but this remains debated. Our goal was thus to better understand the impact of neuroticism through verbal and physiological assessment in response to stimuli inducing fear and sadness as compared to another negative emotion (disgust).¦Methods: Fifteen low neurotic and 18 high neurotic subjects were assessed on an emotional attending task by using film excerpts inducing fear, disgust, and sadness. We recorded skin conductance response (SCR) and corrugator muscle activity (frowning) as indices of emotional expression.¦Results: SCR was larger in high neurotic subjects than in low neurotics for fear relative to sadness and disgust. Moreover, corrugator activity and SCR were larger in high than in low neurotic subjects when fear was induced.¦Conclusion: After decades of evidence that individuals higher in neuroticism experience more intense emotional reactions to even minor stressors, our results indicate that they show greater SCR and expressive reactivity specifically to stimuli evoking fear rather than to those inducing sadness or disgust. Fear processing seems mainly under the influence of neuroticism. This modulation of autonomic activity by neurotics in response to threat/fear may explain their increased vulnerability to anxious psychopathologies such as PTSD (post traumatic stress disorder).

Point defects and texture of Pd1-xInx sputtered intermetallic thin films

Pd1-xInx thin films (0.4 < x < 0.56) were prepared by radio frequency sputtering from a multi-zone target. The properties of these Hume-Rothery alloys were studied by X-ray diffractometry, electron probe microanalysis and scanning tunneling microscopy. The diffraction spectra were analyzed to obtain the intensity ratio of the (100) superlattice line to the (200) normal line, together with the variations of the lattice constant. The results ape explained quantitatively by a model based on point defects, i.e. Pd vacancies in In-rich films and Pd antisite atoms in Pd-rich films. In-rich films grow preferentially in the [100] direction while Pd-rich films grow preferentially in the [110] direction. The grains in indium-rich sputtered films appear to be enclosed in an atomically thick, indium-rich layer. The role of texture and the influence of point defects on electrical resistivity is also reported. (C) 1996 Elsevier Science Limited.

Screen printed La2/3Sr1/3MnO3 thick films on alumina substrates

We report here on the preparation of La2/3Sr1/3MnO3 magnetoresistive thick films on polycrystalline Al2O3 substrates by using the screen printing technique. It is shown that films can be obtained using high temperature sintering. While there is a reacted layer, this improves adhesion and is not too troublesome if the films are made thick enough. It is shown that PbO-B2O3-SiO2 glass additives allow sintering at lower temperatures and can be used to improve the mechanical stress of the films. However, it is found that glass concentrations large enough to significantly improve the film adherence result in a weak low field magnetoresistance probably because grains are coated with high resistivity material. Strategies to overcome these difficulties are discussed.

Optical response of Cu3Ge thin films

We report an investigation on the optical properties of Cu3Ge thin films displaying very high conductivity, with thickness ranging from 200 to 2000 Å, deposited on Ge substrates. Reflectance, transmittance, and ellipsometric spectroscopy measurements were performed at room temperature in the 0.01-6.0, 0.01-0.6, and 1.4-5.0 eV energy range, respectively. The complex dielectric function, the optical conductivity, the energy-loss function, and the effective charge density were obtained over the whole spectral range. The low-energy free-carrier response was well fitted by using the classical Drude-Lorentz dielectric function. A simple two-band model allowed the resulting optical parameters to be interpreted coherently with those previously obtained from transport measurements, hence yielding the densities and the effective masses of electrons and holes.

Le cinéma-vérité, films et controverses

Peut-on se réclamer du « cinéma » tout en prétendant rendre compte d'une « vérité »? Quelles sont les limites éthiques du dévoilement d'un individu face à une caméra ? Un cinéaste peut-il être pleinement « auteur » d'une oeuvre construite à partir de fragments de réel? Voilà quelques-unes des questions posées au début des années soixante par la sortie des films qui se revendiquent ou sont associés au « cinéma-vérité ». Proposée en 1960 par Edgar Morin, cette notion controversée sert durant quelques années de bannière à un mouvement cinématographique supposé renouveler les rapports entre film et réalité par une approche plus directe, un dispositif d'interactions avec les protagonistes, ou une démarche autoréflexive qui interroge en son sein le projet du film. Chronique d'un été de Jean Rouch et Edgar Morin, Les Inconnus de la terre et Regard sur la folie de Mario Ruspoli, les travaux de Richard Leacock pour la Drew Associates, Le Chemin de la mauvaise route de Jean Herman, Hitler, connais pas de Bertrand Blier, La Punition de Jean Rouch ou encore Le Joli Mai de Pierre Lhomme et Chris Marker : tous ces « films-vérité » renouvellent les débats et construisent de nouveaux clivages dans la cinéphilie française. Sans chercher à se positionner sur le contenu des polémiques, le présent ouvrage retrace pour la première fois l'histoire du mouvement « cinéma-vérité » en s'intéressant aux films (contexte de production, tournages, innovations techniques) et aux discours (articles, débats, tables rondes) qui les ont précédés, accompagnés et traversés. Grâce à de nombreuses sources inédites, Cinéma-vérité, films et controverses met au jour un phénomène d'une importance méconnue dans l'histoire du cinéma en France.

Perpendicular magnetic anisotropy in chemically disordered FePd-FeV(100) alloy thin films

We find that the use of V(100) buffer layers on MgO(001) substrates for the epitaxy of FePd binary alloys yields to the formation at intermediate and high deposition temperatures of a FePd¿FeV mixed phase due to strong V diffusion accompanied by a loss of layer continuity and strong increase of its mosaic spread. Contrary to what is usually found in this kind of systems, these mixed phase structures exhibit perpendicular magnetic anisotropy (PMA) which is not correlated with the presence of chemical order, almost totally absent in all the fabricated structures, even at deposition temperatures where it is usually obtained with other buffer layers. Thus the observed PMA can be ascribed to the V interdiffusion and the formation of a FeV alloy, being the global sample saturation magnetization also reduced.

White luminescence from Si+ and C+ ion-implanted SiO2 films

The microstructural and optical analysis of SiO2 layers emitting white luminescence is reported. These structures have been synthesized by sequential Si+ and C+ ion implantation and high-temperature annealing. Their white emission results from the presence of up to three bands in the photoluminescence (PL) spectra, covering the whole visible spectral range. The microstructural characterization reveals the presence of a complex multilayer structure: Si nanocrystals are only observed outside the main C-implanted peak region, with a lower density closer to the surface, being also smaller in size. This lack of uniformity in their density has been related to the inhibiting role of C in their growth dynamics. These nanocrystals are responsible for the band appearing in the red region of the PL spectrum. The analysis of the thermal evolution of the red PL band and its behavior after hydrogenation shows that carbon implantation also prevents the formation of well passivated Si/SiO2 interfaces. On the other hand, the PL bands appearing at higher energies show the existence of two different characteristics as a function of the implanted dose. For excess atomic concentrations below or equal to 10%, the spectra show a PL band in the blue region. At higher doses, two bands dominate the green¿blue spectral region. The evolution of these bands with the implanted dose and annealing time suggests that they are related to the formation of carbon-rich precipitates in the implanted region. Moreover, PL versus depth measurements provide a direct correlation of the green band with the carbon-implanted profile. These PL bands have been assigned to two distinct amorphous phases, with a composition close to elemental graphitic carbon or stoichiometric SiC.