We present a study of the influence of the substrate nano-structure and composition on the morphological properties of the carbon nanotubes (CNTs) by sequentially growing in situ TiNx:Oy film, dispersed nickel catalyst particles, and CNTs obtained by CVD. The results show that the stoichiometry and the nanostructures of the substrate intervene in the growing process. Particular attention is pay to the influence of oxygen on the CNT growths. The results show that O prevents the coarsening of the catalyst nickel particles, avoiding the surface diffusion mobility of the precursor atoms involved in the nanotubes growth (Ostwald ripening)1. The dependence of the size and density of the CNTs on the amount of O present in the substrate are reported and discussed. The experimental findings show that, besides acting as diffusion barrier between the catalyst particles and the silicon, the substrate also influences the kinetics of growth of carbon nanotubes.

The influence of nano-structure and composition of the substrate on the properties of carbon nanotubes (CNTs) is presented. The samples are obtained following a sequential in situ deposition routine. First, TiNxOy films are grown on a crystalline silicon substrate. Immediately, dispersed nickel catalyst particles are deposited on the film. The non-stoichiometric TiNxOy films and Ni particles are grown by ion beam sputtering of Ti and Ni targets, respectively. Soon after that, the CNTs are grown by feeding acetylene gas into the chamber and maintaining the substrate at 973 K. In situ x-ray photoelectron spectroscopy allows compositional and structural analysis in all the stages of the sample growth process. The CNTs are further studied by scanning and transmission electron microscopy techniques, showing different population densities, sizes and diameters as a function of the oxygen content in the TiNxOy films. The results show that oxygen influences the surface diffusion mobility of the precursor carbon atoms involved in the growth of nanotubes suggesting the inhibition of catalyst particle coarsening. It is concluded that, in addition to acting as a diffusion barrier between the catalyst particles and the silicon support, the TiNxOy films modify the growth kinetics of the CNTs.

New techniques in microelectronics allow to build large arrays of bolometers filling the focal plane of submillimeter and millimeter telescopes. The expected sensitivity increase is the key for the next generation of space experiments in this wavelength range. Superconducting bolometers offer currently the best prospects in terms of sensitivity and multiplexed readout. We present here the developments led in France based on NbSi alloy thermometers. The manufacturing process of a 23 pixel array and the test setup are described.

Ion beam sputtering is used for elaborating ferromagnetic Co/Al2O3/Co/NiFe multilayers. The interface state and the roughness of the multilayer are examined by TEM and AFM. The insulating layer is found to be homogenous with a low RMS roughness. Magnetic properties of each electrode and of the full stack are studied by P-MOKE and AGFM. The magnetic behaviour of the full stack is characteristic of two switching fields with a Néel coupling.

Cobalt and alumina layers are deposited by UHV ion beam sputtering to elaborate Co/Al2O3/Co junctions. To form the Al2O3 insulator barrier, oxygen is introduced into the chamber during the aluminum target sputtering. The experimental conditions to obtain stoichiometric Al2O3 are determined using auger electron spectrometer (AES) and Rutherford backscattering spectroscopy (RBS). Stoichiometric Al2O3 is obtained with an oxygen pressure of 6×10−7 mbar, i.e. a deposition rate of 0.5Å/mn, and a beam intensity of 55μA. Magnetic properties of the Co bottom electrode and the mutilayers are studied by magneto-optical Kerr effect (MOKE) and by alternating gradient field magnetometry (AGFM). The easy axis of magnetization is in-plane and the Co layers present an in-plane anisotropy. Moreover, the Co bottom electrode is paramagnetic for a thickness below 40Å, at room temperature.

Magnetoresistance of magnetic tunnel junctions (MTJ: ferromagnetic/insulator/ferromagnetic) has potential applications in magnetic sensors and non volatile memory devices. Magnetoresistance of 40% h as already been obtained by S.S.P. Parkin and al.[1]. The magnetoresistance strongly depends on the exact composition of the layers and the interface propert ies. Therefore, the different layers must be appropriate ly deposited. The development of an efficiently optimi zed oxidation process of the insulator barrier is requi red, because the MTJ device strongly depends not only on intrinsic ferromagnetic electrodes, but also on the insulating barrier [2] [3].

We present a photoelectron spectroscopy study of three single crystal PtxPd1−x(111) alloy surfaces (x=0.1, 0.5, 0.9) using synchrotron radiation. The surface and chemical sensitivity of core level photoemission allows us to quantify an oscillatory depth concentration profile and the palladium segregation at the surface of each alloy. The experimental results are compared to theory based on regular solution and tight binding Ising model formalisms, a good agreement is found. In the second part of the paper the effect of CO adsorption on the alloy surfaces is investigated. The variety of adsorption site geometry and chemistry as a function of surface segregation and bulk alloy concentration is revealed in both valence band and core level spectra.

The growth mode and the structure of Co layers deposited at room temperature (RT) on a Au(111) single crystal has been studied using core level photoemission spectroscopy (CL-PES) and surface X-ray absorption spectroscopy (SEXAFS). The analysis of the Au 4f7/2 photoemission line for different Co coverages provides evidence of an island growth mode with the presence of a slight interdiffusion process at the interface. The polarization dependence of the XANES and EXAFS spectra, taken at the Co K-edge, shows clearly a hexagonal stacking for films thicker than 4ML. The analysis of the first nearest neighbour shell shows that this hexagonal structure is very close to that of the Co hcp bulk: the cobalt films do not grow in a coherent epitaxy on the Au(111) surface and they are then not strongly strained. Thus, we can exclude a magnetoelastic contribution to the perpendicular magnetic anisotropy existing in this system.

The structure of cobalt thin films on an Au(lll) surface has been studied using x-ray absorption spectroscopy at the cobalt K edge. The polarization dependence of x-ray absorption near-edge spectra and extended x-ray absorption fine structure (EXAFS) spectra evidences a hexagonal stacking for films thicker than 4 ML. For all the thicknesses, the analysis of the first-nearest-neighbor shell shows that this hexagonal structure is very close to that of the Co hcp bulk one: the cobalt does not grow in a coherent epitaxy on the Au(lll) surface. This incoherent epitaxy leads to a wide radial distribution of the Co-Au bonds at the interface: this effect and the contribution of Au atoms to the EXAFS signal are discussed. The weak strains inside the Co magnetic thin films allow us to neglect the contribution of the magnetoelastic anisotropy to the perpendicular-magnetic anisotropy existing in this system. [S0163-1829(99)00703-1].

The growth of Co layers deposited at room temperature on a Au(111) single-crystal has been studied by means of synchrotron radiation induced angle resolved photoemission spectroscopy (PES). The surface and bulk components of the Au 4f72 photoemission line were analyzed as a function of Co coverage. From the evolution of the positions and intensities of the different contributions of the Au 4f72 line one can deduce an island growth below two monolayers (ML) coverage. Above 2 ML, the completion of the interstices between islands starts and the surface is completely covered slightly above 3 ML. A third component appears above 2.2 ML in the photoemission line and is attributed to interdiffusion between the Co overlayer and the Au substrate.

The room temperature deposition of Sb on to Cu (111) gives rise to two different Sb states as seen from the Sb 4d shallow core level: an adstate similar to the [Formula: see text] structure formed after annealing at 400°C, and an overlayer of unreacted Sb . The unreacted Sb overlayer is rapidly dissolved into a subsurface position in the crystal during annealing, where it forms a quasistable structure which is dissolved very slowly.

we have analysed by means of synchrotron radiation induced angle resolved photoemission spectroscopy (PES) and Auger electron spectroscopy (AES) the growth of Cobalt layers deposited at room temperature on a Au(111) surface. We have studied the behaviour of the Au 4f (7/2) photoemission lines (bulk peak at 84 eV, surface peak at 83.65 eV in binding energy) and Auger transitions (Au NW at 69 eV, Co MW at 53 eV). The analysis of the Au 4f (7/2) photoemission core level, for several thicknesses, shows core level shifts corresponding to different environments for the Au atoms. From the evolution of the positions and intensities of the different contributions of Au 4f (7/2) line, three stages in the growth of Co on Au (111) can be deduced. Up until 1 monolayer (ML) of Co deposited, we observe a regular attenuation of the surface line corresponding to a three-dimensional growth : only half of the surface is covered. Between 1 and 2 ML, the uncovered surface does not change : the height of the islands increases. Above 2 ML; the coalescence of islands starts and a third component appears in the photoemission line at a binding energy of 84.4 eV which can be attributed to an interdiffusion between the Co overlayer and the Au substrate at the interface.