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The carbonization process of a single domain 2{times}1-reconstructed Si(001) vicinal surface (5{degree} off axis from [001] in the [{bar 1}10] direction) in acetylene has been studied by combining in situ surface science techniques (x-ray photoemission spectroscopy, x-ray photoelectron diffraction, reflection-electron energy loss spectroscopy, low-energy electron diffraction) and ex situ analytical techniques ({sup 12}C and {sup 2}H dosing by nuclear reaction analysis, scanning electron microscopy, and reflection high-energy electron diffraction). It is found that at a growth temperature of about 820{degree}C a variety of growth mechanisms can be observed, particularly during the first step of carbonization. An analysis of C1s and Si2p core-level shifts and of the respective intensities of them, combined with the examination of photoelectron diffraction curves, gives evidence for a penetration of C atoms into the silicon substrate, to form a nonstoichiometric compound. Contemporaneously 3C-SiC nuclei form, aligned with respect to the substrate. Then a quasicontinuous 3C-SiC film grows heteroepitaxially (cube on cube unstrained growth) on the substrate up to a thickness of {approximately}40{Angstrom}. C1s and Si2p photoelectron diffraction patterns, compared with calculated ones, show that the single domain initial surface does not necessarily force a preferential alignment of one of the two inequivalent SiC{l_brace}110{r_brace} planes with respectmore » to the (110) Si plane. Consequently, such vicinal Si(001) surfaces are not necessarily templates for the growth of crystalline films free of antiphase boundary domains. Finally, we have observed that an imperfect coalescence of 3C-SiC nuclei leaves easy paths for Si out migration from the substrate and SiC polycrystalline growth, even at a temperature as low as 820{degree}C. The current models of Si(001) carbonization are examined and compared to our experimental findings. (Abstract Truncated)« less

Synchrotron radiation X-ray photoemission spectroscopy (SRXPS), used with an optimized surface and interface sensitivity, is a unique tool to determine the chemical composition and spatial extension of the suboxide layer present at the Si/SiO2 interface. The bonding at ‘thermal interfaces’ appear to be essentially dependent on the Si crystal orientation. For Si(001)/SiO2 a detailed photon energy-dependent and angle-dependent. SRXPS study (in the 120 ÷ 175 eV photon energy range) has been performed. Previous results on higher-oxidation states cross-section resonances around hv = 130 eV are re-examined. The various oxide states do not present photoelectron diffraction peaks, when polar scans are performed in the (110) azimuthal plane. On the other hand, there is evidence that substrate silicon atoms close to the interface retain orientational order. Limits in the vertical distribution of the suboxides are given. The compatibility of our experimental findings with models of the current literature — in particular the so-called ‘dimerized interface’ model — is examined.

The growth mode of metal phthalocyanines (MPc, MNi, Cu) on clean Cu(001) and Si(001) (i.e. bonding and adsorption geometry) and their electronic structure are studied by a combination of spectroscopic techniques: x-ray photoemission, x-ray absorption at Metal L 2,3 edges and scanning tunnelling microscopy.

The resistance of the As-terminated Si(001) surface to oxidation in O 2 is the subject of this study. Photoemission spectra of As3d and Si2p core levels excited with synchrotron radiation reveals that spectral changes are evident, simultaneously for As and Si, only from ∼10 12 L (Langmuir) on, in stark contrast with a previous report indicating a saturation coverage in the 400–2000 L range. Oxidation proceeds slowly, as dimerized As remain intact (∼24%) up to exposures of ∼10 13 L. In the oxidized areas, the four Si oxidation states (indicative of subsurface oxidation) and three As oxidation states plus metallic arsenic show up. This suggests a reduction of the arsenic oxide by silicon. Arsenic losses are also observed, probably via sublimation of As 4 O 6 molecules.

The strong resistance of the As-terminated Si(001) surface to oxidation in molecular oxygen at room temperature is the subject of this study. As 3d and Si 2p photoemission spectra, as well as valence band spectra, excited with synchrotron radiation (135 eV ≤ hv ≤ 165 eV), have been recorded as a function of increasing O2 exposures, over the range 2400–1.4 × 1013 L (langmuir). Spectral changes, simultaneously observed in the As 3d and Si 2p core-levels near ∼ 1012 L are indicative of the onset of oxidation. However a modification of the valence band, due to the contribution of O 2p states, is clearly evident from ∼ 1011 L, pointing to the presence of weakly bound oxygen species at that exposure. These results are confronted with a previous Auger study reporting an oxygen saturation coverage (0.5 monolayer) already in the 400–2000 L range, interpreted as the insertion of an oxygen atom between two dimerized arsenic atoms. On the contrary our data show that surface oxidation is a slow process, spatially inhomogeneous, as some dimerized As remain intact (∼ 24%) up to exposures as large as ∼ 1013 L. Oxidation is not limited to the outermost layer, as three arsenic oxidation states and the four silicon oxidation states (indicative of subsurface oxidation) are detected simultaneously. Moreover metallic arsenic shows up: this suggests a reduction of the arsenic oxide by silicon. Arsenic losses are also observed, probably via sublimation of As4O6 molecules.

The chemical bonding and molecular orientation of copper phthalocyanine (CuN 8 C 32 H 16 ), deposited on clean single crystal silicon substrates of (111) and (001) orientation, were studied using X-ray photoemission spectroscopy (XPS) of the Cu 2p, C 1s, and N 1s core-levels and synchrotron radiation X-ray absorption spectroscopy (XAS) at the Cu L 2,3 edges. In the monolayer range, the strong interaction of the molecule with the Si (111) surface is mostly evidenced by changes in the Cu 2p XPS spectra that indicate a partial reduction (up to 30%) of the Cu(II) atoms to Cu 3d 10 . The linear dichroism of the XAS spectra shows that those molecules, whose copper is still Cu(II), lie down on the surface. On the other hand, the bonding of the molecule on Si(001) is weaker, as Cu 2p XPS spectra do not exhibit Cu(II) reduction, while XAS spectroscopy indicates a random orientation of the molecules with respect to the surface. N 1s XPS spectra exhibit, on both surfaces, very intense satellites which present, on Si(111), a sharp dependence on the electron take-off angle. With the growth of thicker films, the XPS line shapes of the molecular solid are recovered, and the average tilt angle of the molecules (around 70°) does not depend on the chosen Si surface. We conclude that the structure of the first deposited layer strongly depends on the specific substrate, but does not affect the successive growth of thick layers.

We report the results of a retrospective study of a group of 27 patients with a myopathy who were ventilated at home using a nasal mask over a period of 5 years. Twelve patients were ventilated in a preventive fashion before any orthopaedic surgical intervention and 15 out of necessity because of respiratory failure and/or hypercapnia. There was a statistically significant improvement in the PaO2 while the PaCO2 remained stable. The vital capacity (CV) was unaltered. Side effects were relatively frequent but did not lead to this method of ventilation being stopped. One patient died from a very advanced cardio-myopathy after having stopped his own assisted ventilation. Another patient died at home of bronchial congestion. One patient had a tracheotomy after 3 years of ventilation. The treatment was judged overall as positive amongst the 19 patients who responded to a questionnaire anonymously. We are able to confirm the efficacy of this mode of ventilation by the nasal route as much therapeutically as prophylactically, which is against the recently reported results in a multi-centre study.

Resume Les auteurs decrivent l'observation d'un sujet agamma-A-globulinemique dont le serum contient un anticorps anti-IgA, a specificite de classe. Des transfusions de sang total et des injections intra-musculaires de gammaglobulines ont provoque des reactions immediates, de type anaphylactique. Des transfusions lentes de sang lave ont ete assez bien supportees. Des reactions moins intenses, de type anaphylactoide, ont ete signalees par certains auteurs. Ces observations attirent l'attention sur les points suivants : -- la surveillance des polytransfuses et la recherche systematique d'anticorps anti-immunoglobulines et en particulier anti-IgA devant toute reaction transfusionnelle non hemolytique, en particulier de type anaphylactique ou anaphylactoide, non expliquee par une allo-immunisation anti-leucocytaire ou anti-plaquettaire ; -- la conduite a tenir devant des reactions transfusionnelles de ce type ; -- la constitution d'une reserve de sang total provenant de sujets agamma-A-globulinemiques, congelee a basse temperature ; -- la preparation de gammaglobulines exemptes d'IgA ; -- la prevention de la maladie hemolytique du nouveau-ne, a l'aide des gammaglobulines anti-D, pose un probleme particulier.

Since 1970, 168 patients, mostly of the obstructive type, received an apparatus of assisted ventilation at home, according to the degree of their hypoxia-hypercapnia, following one or several acute failures. Oral ventilation, at a daily minimum of 90 min, distributed in 4 to 8 sessions, was continued for variable duration, from 1 to 5 years. The results, analysed statistically for 40 subjects, show a blood-gas improvement greater in patients whose PaO2, PaCO2 and RV/TC ratio were initially lower. For 17 patients controlled before and after assisted ventilation at home, a reduction in the number of days of hospitalization and acute failures was observed. The cost involved was particulary economical because of the simplicity of the equipment and the possibilities of control of patients and apparatus at the C.H.U. (20 F monthly in 1977 for 145 selected patients).

The thermal growth of 3CSiC films at 820°C in acetylene (chosen among other hydrocarbons because of its high reactivity with Si) was performed and the resulting films were analyzed by nuclear reaction analysis (NRA), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Films were grown on clean single domain 2 × 1 reconstructed Si (0 0 1) vicinal surfaces either in natural (C2H2) or in 99% deuterium enriched (C2D2) acetylene under 2 × 10−6Torr. In order to characterize the electronic structure and the short range order of the films, XPS and its by-product X-ray photodiffraction (XPD) were performed in situ in an analysis chamber connected to the preparation chamber. The growth kinetics was followed by measuring, ex situ, the amount of incorporated carbon using the 12C(d,p)13C reaction at 970 keV, while for determining the hydrogen incorporation in the films the D(3He,p)4He reaction at 700 keV was used. Also ex situ, the film morphology was followed by SEM as the thickness of the layer increased. By using these complementary techniques, phenomena like H incorporation, C in-diffusion and 3CSiC nucleation have been evidenced at the very beginning of the growth (amount of 12C incorporated in the films smaller than 1016 atoms/cm2). Besides, it was observed that the imperfect coalescence of 3CSiC nuclei determine the morphology of films grown during longer times.