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1997 (1)
1983 (1)
1Author    Valerie Bertagna, Francis Rouelle, Marius ChemlaRequires cookie*
 Title    Copper Contamination Mechanism of Silicon Substrates from HF Solutions  
 Abstract    The contamination of silicon wafers from dilute HF solutions containing ultratrace levels of metallic ion impurities is a subject of constant interest. The mechanism of copper electroless deposition from HF onto monocrystalline silicon was investigated using a new electrochemical cell, which proved to be a very sensitive detector for in situ characterization of silicon surfaces. Upon addition of copper trace amounts, the open-circuit potential was observed to shift rapidly towards more positive values at a rate nearly proportional to the copper concentration. All poten-tial/time curves tend to reach a limiting value of the potential, while quantitative measurements of radioactive tracers revealed that during a few tens of minutes, copper ions were continuously reduced on the silicon surface. Electrochemical potentials and voltammetric measurements were interpreted in terms of the mixed potential theory and led to the conclusion that copper nuclei act as a catalyst which enhances the cathodic activity for protons reduction. The model was supported by AFM observations which demonstrated the initiation of corrosion pits around the nuclei. 
  Reference    Z. Naturforsch. 52a, 465—176 (1997); received April 14 1997 
  Published    1997 
  Keywords    Silicon, contamination, copper, catalysis 
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 TEI-XML for    default:Reihe_A/52/ZNA-1997-52a-0465.pdf 
 Identifier    ZNA-1997-52a-0465 
 Volume    52 
2Author    Britta Verhoek, RenateKäthe Haas, Michael Wrage, Linscheid, Ernst HeinzRequires cookie*
 Title    Lipids and Enzymatic Activities in Vacuolar Membranes Isolated via Protoplasts from Oat Primary Leaves  
 Abstract    Vacuoles were released from oat (Avena sativa) mesophyll protoplasts and purified by sed i­ mentation and flotation. Disruption o f isolated vacuoles follow ed by density gradient centri­ fugation gave two m embrane bands which after com bination were further purified on sucrose gradients. A significant contam ination by microbodies, thylakoids, m itochondria, endoplasm ic reticulum and Golgi membranes can be excluded, whereas markers for plasma m em brane and chloroplast envelope were present in the final membrane preparation. In the purified membrane fraction the follow ing enzym atic activities were detected: N A D H -cytochrome C reductase E.C., ATPase E.C., UD PG : sterol glucosyltransferase, UDP-Gal: diacylglycerol galactosyltransferase E.C., glucan synthetase II, C D P-choline: diacylglycerol phosphocholinetransferase E.C., formation o f acylgalactosyl diacylglycerol and acyl-CoA thioesterase E.C. N on e o f these can be considered to be sp ecific for the tonoplast. Acid phosphatase E.C. was present in the cell sap. The vacuolar membranes contain phospholipids and glycolipids o f the most com plex com posi­ tion found so far in a membrane system isolated from m esophyll protoplasts. About h alf o f the glycolipids were accounted for by glycosyl diacylglycerols usually considered to be confined to plastids. Steryl glycosides and acyl steryl glycosides were other prominent glycolipids. A cere-broside was the predominating lipid com ponent o f this membrane preparation. 
  Reference    Z. Naturforsch. 38c, 770—7 (1983); received May 5 1983 
  Published    1983 
  Keywords    Contamination, Microsomal Enzymes, G alactolipids, Steryl G lycosides, Cerebrosides 
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 TEI-XML for    default:Reihe_C/38/ZNC-1983-38c-0770.pdf 
 Identifier    ZNC-1983-38c-0770 
 Volume    38