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2000 (1)
1997 (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    J.Nomssi Nzali, W. HoyerRequires cookie*
 Title    X-ray Investigations of Liquid Bismuth-Copper Alloys  
 Abstract    Liquid copper, bismuth, and eleven bismuth-copper alloys were investigated at temperatures above the liquidus with X-ray diffraction. The experimental procedure was adjusted to reduce the effects of evaporation. The Faber-Ziman total structure factors S(Q) feature a splitting of the first maximum and negative values for Q around 1 A -1 in a large concentration range. The results are compared to previous neutron diffraction results by Zaiss and Steeb, to square-well potential model calculations by Gopala Rao and Satpathy and to a simple segregation model. The segregation model reproduces the features qualitatively. Partial structure factors are assessed by fitting both neutron and X-ray scattering results with reverse Monte-Carlo simulation. 
  Reference    Z. Naturforsch. 55a, 381—389 (2000); received May 29 1999 
  Published    2000 
  Keywords    Bismuth, Copper, Liquid Alloys, X-ray Diffraction, Microsegregation 
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 TEI-XML for    default:Reihe_A/55/ZNA-2000-55a-0381.pdf 
 Identifier    ZNA-2000-55a-0381 
 Volume    55