The preparation of very flat surfaces of silicon by electropolishing

Slices of silicon can be very successfully polished by anodic dissolution in a cell using a horizontal rotating disk as cathode, a viscous electrolyte, and a very small anode-cathode spacing (e.g. 150 μ). The surfaces of n-type material of resistivity > 0·05 Ω-cm must be illuminated during polishing, necessitating perforation of the disk to admit a beam of light to them. The optimum cell voltage is always above that for which the differential conductance of the cell is negative, and is usually about 10 V. The dissolution of 50 μ from a surface initially lapped or mechanically polished leaves it very flat and free of all work damage; electron micrographs show the residual local departures from flatness to be <0·01 μ. Material so prepared offers advantages in planar technology and as substrates for epitaxial growth. A full quantitative understanding of the mechanisms involved is still lacking however.     

Die direkte gewichtsanalytische Bestimmung der Bors?ure in Nahrungsmitteln

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Bier

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Beitr?ge zur Zersetzung der Futter- und Nahrungsmittel durch Kleinwesen

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