Characterization of Cu-Sn/Pb diffusion zones of microelectronic contacts by means of electron probe microanalysis and ion beam sputtering

Physical parameters of material, such as strength and electrical conductivity, can be influenced considerably by the intermetallic compounds formed by diffusion in soldered microelectronic contacts between Cu and Sn/ Pb solders. Therefore, formation and growth of these contact zones were systematically investigated on model specimens in dependence on temperature, time and chemical tin-lead concentration of the solders by means of electron probe microanalytical investigations and characterized by phase growth constants. Compared with the conventional metallographic specimen preparation method, the ion beam etching of the contact surfaces proves to be an excellently suitable means for representing the microstructure after the cooling of the samples. Moreover, the three-dimensional grain structure and technologically caused defects in the contact can be shown by ion beam slope cutting. Effects as e.g. the dendritic growth and Kirkendall pores which increasingly occur at higher temperatures are successfully proved.     

Modular transformations ofSU(N) affine characters and their commutant

We describe the algebra of matrices commuting with the action of the modular group on characters ofSU(N) _k integrable representations. Using methods of finite quantum mechanics we find a canonical basis for this commutant over and prove the existence of an equivalent basis over with integral matrix elements. A final section is devoted to the case ofSU(3).Laboratoire de l'Institut de Recherche Fondamentale du Commissariat à l'Energie Atomique     

Investigation of laser-induced plasma deposition of boron nitride

Laser ionization mass spectrometry (LIMS) was applied to the investigation of the composition of laser plasmas of three different boron nitride modifications (hexagonal -boron nitride with graphite structure, cubic -boron nitride with diamond structure and hexagonal -boron nitride resembling the wurtzite type). Thin films in the 10 nm range were produced in the ion source of the laser mass spectrograph by laser-induced plasma deposition. So we could carry out the plasma diagnostic and the preparation of thin films under the same condition. The cluster distribution in laser plasma is independent of the structure of the BN target. An explanation of laser-induced plasma deposition of boron nitride from the results of mass spectrometric analysis of laser plasmas and of the analysis of deposited thin films (TEM, EELS) was derived.     

Hetero-Cope-Umlagerungen. 4. Mitteilung. Regiokontrollierte Indolsynthesen

Hetero-Cope-Rearrangements, Regio-Controlled Synthesis of Indoles The reaction of O-deprotonated N-phenylhydroxylamines 1 with various electron-deficient allenes 2 , 14 , 16 gives, via Michael addition and Cope-rearrangement, substituted anilines 5 , which are easily convertible into indoles 6 . In this manner, sulfoxides 17 , serve as equivalents of 2-vinylindoles. Diels-Alder reaction with this 2-vinylindole equivalent followed by indolisation affords isoquinuclidine derivative 21 which may be a useful precursor for the preparation of Iboga alkaloids.     

Osmotic and activity coefficients of aqueous bile salt solutions at 25, 37, and 45°C

Osmotic coefficients measured by vapor pressure osmometry are reported for aqueous bile salt solutions at 25, 37, and 45°C. Solute activities decrease rapidly with increasing concentration due to premicellar association and micelle formation. In all cases, activities of the dihydroxy bile salts are lower than those of the trihydroxy bile salts. Osmotic coefficients and activity coefficients increase with increasing temperature. It is suggested that hydrophobic forces contribute substantially to the stability of primary bile salt aggregates and micelles.