Photo-stimulated CVD of SiNx for GaAs IC applications

The characteristics of silicon nitride deposited by a photo-enhanced CVD process have been investigated. The nitride films are used as inter metal insulator in GaAs ICs. For this application the step coverage is the most crucial aspect. The photo-CVD of SiN_x proves to be a surface determined deposition process, even in the case of undercutted structures. The insulation between first and second metallization was measured on a contact test structure with 1800 cross-overs. The insulating resistance in this structure is in the GΩ range even if the nitride is only 300 nm thick. A thickness uniformity of 4% for a batch of six 3 inch wafers and a reproducibility of 5% were obtained for 300 nm thick films, the intrinsic tensile stress being as small as 10⁷ to 10⁸ dyn/cm². The threshold voltage shift due to deposition was only -25 mV for MESFETs in GaAs ICs.     

Nouvelles syntheses de Me2SiCl2 et Me3SiCl

Partial reduction of MeSiCl₃ and Me₂SiCl₂ using CaH₂ or (TiH₂)_n at high temperature (300°C) leads to MeSiHCl₂ and Me₂SiHCl, respectively, in good yields but in low proportion. In the presence of AlCl₃ as catalyst the reaction affords Me₂SiCl₂ and Me₃SiCl, in yields higher than those previously observed in the absence of a reducing agent. These redistribution reactions involve MeSiHCl₂ and Me₂SiHCl as intermediates. Consequently Me₂SiHCl with or without Me₂SiCl₂ and Alcl₃ deposited on carbon black as catalyst can undergo disproportionation to give Me₃SiCl.     

Die Normalisierung komplexer Räume

Ohne Zusammenfassung     

Differentiation of wool and spruce waxes affected by environmental influences using fingerprinting by soft ionization mass spectrometry

Summary Wool wax from two sheep which showed different susceptibility towards fleece rot was analysed by field desorption mass spectrometry. In the mass range from m/z 360 to m/z 410 clear differences of ion abundances were found indicating lower proportions of oxidized cholesterone in the wax of the resastent sheep. This suggests that the weathering of the fleece wax could be a factor in relation to the cause of fleece rot.Epicuticular wax isolated from green and yellowish Norway spruce needles was analysed by field ionization mass spectrometry. The comparison of the both mass spectra in the range from m/z 70 to m/z 1000 demonstrates that the wax layer of conifer needles is altered by air pollution resulting in higher proportions of free n-fatty acids and estolides. This corresponds to a premature ageing of the epicuticular wax.Both examples demonstrate that soft ionization mass spectral fingerprints of raw waxes of animals and plants can be used for a rapid characterization and differentiation of untreated and complex, biological samples.

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Unterscheidung von Woll- und Fichten-Wachsen nach Umweltschädigung mit Fingerabdruck-Massenspektren nach schonender Ionisierung

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Field desorption mass spectrometry of lipids IV, for Part I–III, see refs. [5–7]     

Homotopiemengen von Multiplikationen auf Sphären und ihre algebraische Struktur

In an earlier paper [E4] we introduced an algebraic structure on sets of homotopy classes [S ^p ×S ^q ;S ⁿ ], given by the reflecting product on spheresS ⁿ , which makes these sets symmetric groupoids. In this article we determine precisely the algebraic structure of the symmetric groupoids ([S ⁿ ×S ⁿ ;S ⁿ ], ) forn 1, 3, 7.