Solid-phase epitaxy of CaSi2 on Si(1 1 1) and the Schottky-barrier height of CaSi2/Si(1 1 1)

Thin Ca films were evaporated on Si(1 1 1) under UHV conditions and subsequently annealed in the temperature range 200–650 °C. The interdiffusion of Ca and Si was examined by ex situ Auger depth profiling. In situ monitoring of the Si 2p core-level shift by X-ray photoemission spectroscopy (XPS) was employed to study the silicide formation process. The formation temperature of CaSi₂ films on Si(1 1 1) was found to be about 350 °C. Epitaxial growth takes place at T≥400 °C. The morphology of the films, measured by atomic force microscopy (AFM), was correlated with their crystallinity as analyzed by X-ray diffraction (XRD). According to measurements of temperature-dependent I–V characteristics and internal photoemission the Schottky-barrier height of CaSi₂ on Si(1 1 1) amounts to qΦ_Bn=0.25 eV on n-type and to qΦ_Bp=0.82 eV on p-type silicon.     

Linear differential-algebraic equations with properly stated leading term: Regular points

We consider in this work linear, time-varying differential-algebraic equations (DAEs) of the form A(t)(D(t)x^′(t))+B(t)x(t)=q(t) through a projector approach. Our analysis applies in particular to linear DAEs in standard form E(t)x^′(t)+F(t)x(t)=q(t). Under mild smoothness assumptions, we introduce local regularity and index notions, showing that they hold uniformly in intervals and are independent of projectors. Several algebraic and geometric properties supporting these notions are addressed. This framework is aimed at supporting a complementary analysis of so-called critical points, where the assumptions for regularity fail. Our results are applied here to the analysis of a linear time-varying analogue of Chua's circuit with current-controlled resistors, displaying a rich variety of indices depending on the characteristics of resistive and reactive devices.     

On the full holonomy group of Lorentzian manifolds

The classification of restricted holonomy groups of \(n\) -dimensional Lorentzian manifolds was obtained about ten years ago. However, up to now, not much is known about the structure of the full holonomy group. In this paper we study the full holonomy group of Lorentzian manifolds with a parallel null line bundle. Based on the classification of the restricted holonomy groups of such manifolds, we prove several structure results about the full holonomy. We establish a construction method for manifolds with disconnected holonomy starting from a Riemannian manifold and a properly discontinuous group of isometries. This leads to a variety of examples, most of them being quotients of pp-waves with disconnected holonomy, including a non-flat Lorentzian manifold with infinitely generated holonomy group. Furthermore, we classify the full holonomy groups of solvable Lorentzian symmetric spaces and of Lorentzian manifolds with a parallel null spinor. Finally, we construct examples of globally hyperbolic manifolds with complete spacelike Cauchy hypersurfaces, disconnected full holonomy and a parallel spinor.     

Direct injection of biological fluids: Application of HPLC-analysis with precolumn enrichment to the pharmacokinetic studies of lonazolac

Summary Lonazolac and its p-hydroxylated metabolite M1 are determined in serum by high performance liquid chromatography using direct injection of comparatively large volumes with precolumn enrichment. No sample workup is required prior to analysis. Reproducibility, calibration plots, recoveries and detection limits are presented, together with various applications of the method. Data from direct injection of serum are also compared to results from a conventional extraction work-up.Presented at the 14th International Symposium on Chromagraphy London, September, 1982     

Analytical,structural and electrical characterization of SiGe layers by electron microbeam techniques

k-ratios of Ge-L and Si-K measured at different beam energies allow to evaluate simultaneously composition and thickness of SiGe layers on a Si substrate. A simple technique applying backscattered electrons also enables estimation of composition of bulk SiGe and of composition and thickness of relatively thick (200 nm) SiGe layers on Si. Electron channeling patterns of pseudomorphic SiGe/Si structures and of pure Si substrate show no significant differences whereas in relaxed structures a smearing of the pattern with increasing density of misfit dislocations is observed. Under particular conditions the technique of the electron beam induced current permits imaging of recombination-active misfit dislocations with a spatial resolution around 0.2 m. Moreover, a repulsion of holes due to the valence-band offset in a n-Si/SiGe heterostructure was detected.     

The cofinality of the strong measure zero ideal for κ inaccessible

We investigate the cofinality of the strong measure zero ideal for κ inaccessible and show that it is independent of the size of 2^κ.     

Reaktionshemmender Einflu? von Schwefel auf die Aufkohlung von Nickel in Methan-Wasserstoff-Gemischen

Summary The carburization of nickel in CH₄-H₂ and CH₄-H₂S-H₂ gas mixtures was studied in a flow apparatus at 1060–1280 K applying the resistance-relaxation technique. The reaction of nickel with CH₄ is found to be thermally activated with an activation energy of 128 kJ/mol. The ratecontrolling step is the separation of the first hydrogen atom from the CH₄-molecules impinging on the surface. Small H₂S-amounts, resulting in PH₂S/PH₂-ratios between 8 × 10^–9 and 9 × 10^–5 decrease the initial carburization rate by a factor of up to 100. The kinetic data are interpreted in terms of poisoning of active surface sites by adsorbed sulfur. From this analysis adsorption isotherms for sulfur are derived.