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Djokic S.S.,Elchem Consulting Ltd. | Djokic N.S.,Elchem Consulting Ltd. | Guthy C.,University of Alberta | Thundatb T.,Elchem Consulting Ltd.
Electrochimica Acta | Year: 2013

Deposition of copper, silver and gold from aqueous solutions onto germanium substrates is studied inthis work. For this purpose both acidic and alkaline solutions were used. All investigated metals cansuccessfully be deposited via the galvanic displacement reaction. These deposits are porous and withdifferent surface morphologies which depended on the type (p- or n-) of the Ge substrate used in theexperiments and on pH. Prolonged times of immersion of Ge substrates into investigated solutions maylead to a formation of more porous coatings and even powders, as successfully demonstrated on theexample of silver. It is believed that the approach presented in this work should further be investigatedas an activation step for a possible metallization of Ge substrates via autocatalytic or electrodepositionmethods. © 2013 Elsevier Ltd. All rights reserved.

Djokic S.S.,Elchem Consulting Ltd. | Cadien K.,University of Alberta
ECS Electrochemistry Letters | Year: 2015

Direct deposition of silver from fluoride-free alkaline solutions containing Ag(I) ions at pH higher than 12 onto silicon surfaces at room or elevated temperatures has been demonstrated. This deposition does not require a reducing agent, i.e. process proceeds via galvanic displacement reactions. This new process that is based on strong alkaline and fluoride-free solutions was experimentally illustrated through XRD and SEM analyses. Theoretically, it was confirmed that this process is thermodynamically favorable at room temperature, however for the real industrial applications elevated temperatures (up to 100 °C) are recommended. © The Author(s) 2015. Published by ECS.

Djokic S.S.,Elchem Consulting Ltd. | Djokic N.S.,Elchem Consulting Ltd. | Thundat T.,University of Alberta
Journal of the Electrochemical Society | Year: 2012

Deposition of bismuth powders was investigated in this work. Bi powders can be obtained from heterogeneous systems e.g., via galvanic displacement reaction by an immersion of aluminum metal into Bi(III) complexed solutions. It was shown that, on the aluminum substrate, Bi powders can be obtained from acid, close to neutral or from alkaline solutions. Bi particles obtained via galvanic deposition are predominantly dendritic. To avoid the incorporation of Bi - oxides into the final product, it is recommended that the deposition via galvanic displacement reaction from K[BiI4] or complexed Bi(III)-citrate-EDTA solutions on Al substrate is carried out in the acidic solutions in order to suppress the hydrolysis of Bi(III) ions. Alternatively, bismuth powders can successfully be produced from homogenous aqueous systems using Bi(III) complexed solutions as a source of Bi and an alkaline Sn(II) solution acting as a reducing agent of Bi(III) ions. The average particle size was about 0.25 μm for Bi powders produced from Bi(III) - citrate complexed solution using alkaline Sn(II) as a reducing agent. For Bi powders produced from K[BiI4] solutions with Sn(II) as a reducing agent, the average particle size was estimated at about 0.65 μm. © 2012 The Electrochemical Society.

Djokic S.S.,Elchem Consulting Ltd. | Prashanthi K.,University of Alberta | Thundat T.,University of Alberta
Electrochemical and Solid-State Letters | Year: 2012

Thin black films composed of bismuth and respective iodides, i.e. CuI and AgI can be produced upon an immersion of copper or silver substrates into KBiI 4 solutions. The reactions leading to the formation of black films onto copper or silver surfaces into KBiI 4 solutions are spontaneous at the standard physico-chemical conditions, as evidenced by the thermodynamic data. © 2012 The Electrochemical Society.

Gaikwad R.,University of Alberta | Djokic S.S.,University of Alberta | Djokic S.S.,Elchem Consulting Ltd. | Thundat T.,University of Alberta
Journal of the Electrochemical Society | Year: 2015

A lithography technique based on reduction of metal ions on localized regions of GaAs surfaces is demonstrated. In this technique, an atomic force microscopy (AFM) tip was used to create localized defect patterns on a GaAs surface while operated in air. Subsequent exposure of the semiconductor surface to an Au(III) solution results in the deposition of gold by galvanic displacement reaction on pre-patterned defect areas. Random formation of gold islands outside of the pattern is eliminated by restricting the contact time between the Au(III) solution and GaAs semiconductor to approximately 5 minutes. © The Author(s) 2015. Published by ECS.

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