The infrared transmission spectra of two 'polysilanes' of approximate composition (SiH,), and (SiH),, prepared by chemical means, have been measured in the range 4000 to 650 cm-1. The appearance of new bands in the infrared spectra during the oxidation of films of these materials by exposure t o air is interpreted in terms of changes in thelocal environment around the silicon-hydrogen moieties. It is demonstrated that the wave number of the silicon-hydrogen stretching modes of SiH and SiH, groups vary systematically with the number and electronegativity of the next neighbouring atom. The influence of the inductive effect on the stretching frequencies can be empirically related, following the methodology of Lucovsky, to the Pauling electronegativity sum of the adjacently bound oxygen atoms. The infrared band frequencies exhibited in the oxygenated 'polysilane' samples correspond exactly with bands that arise during the exposure of certain undoped and P-doped hydrogenated a-Si films to air. Ageing phenomena produced in r.f. discharge a-Si films are associated with the porosity and oxidation of a hydrogen rich phase in the amorphous material.Die Infrarottransmissionsspektren zweier chemisch hergestellter ,,Polysilane" der Zusammensetzung (SiH2), und (SiH), wurden im Bereich 4000 bis 660 cm-1 gemesaen. Das Auftreten neuer Banden im Infrarotspektrum wahrend der Oxidation der Schichten durch Aussetzen dieser Materialien an Luft wird mit dnderungen der lokalen Umgebung urn die Silizium-WassemtoffHalften erklart. Es wird gezeigt, daB die Wellenzahl der Silizium-Wasserstoff-Stretching-Moden von SiH-und SiH,-Gruppen sich systematisch mit der Zahl und Elektronegativitiit der n&chsten Nachbaratome Lndert. Der EinfluB des induktiven Effekts auf die Stretchingfrequenz liiBt sich empirisch, nach der Methodologie von Lucovsky, mit der Summe der Paulingschen Elektronegativitat der benachbarten gebundenen Sauerstoffatome verkniipfen. Die Frequenzen der in den sauerstoffbehandelten ,,Polysilan" -Proben auftretenden Infrarotbanden stimmen exakt mit Banden iiberein, die wlhrend der Einwirkung von Luft auf einige undotierte oder p-dotierte, wasserstoffbehandelte a-Si-Schichten auftreten. Alterungserscheinungen in HF-Entladungs-a-Si-Schichten werden mit der Porositat und der Oxidation einer wasserstoffreichen Phase im amorphen Material verkniipft.
The effects of the presence of a uniform magnetic field on the growth rate and the threshold intensity of the two-plasmon decay in a homogeneous plasma have been investigated. Analytical expressions for the growth rate and threshold intensity have been obtained. It has been shown that the presence of a magnetic field affects significantly the growth rate and the threshold intensity for the two-plasmon decay.
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