COMPOSITIONALLY MODULATED COBALT-TUNGSTEN ALLOYS DEPOSITED FROM A SINGLE AMMONIACAL ELECTROLYTE

Electrodeposition of Co-W alloys and the possibility for compositional modulation from single ammoniacal electrolytes were studied. The infl uence of pH, current density, W:Co ratio, tartrate concentration and t emperature on the composition of the deposit and the cathode current e fficiency were investigated by a Taguchi experimental plan. It was fou nd that the alloy composition is sensitive to solution chemistry, curr ent density and temperature. It has also been shown that it is possibl e to reduce the tungsten content in the deposit by current modulation and the use of anodic pulses during deposition, i.e. selective etching . With cross-sectional TEM analysis, it has been sho cvn that the sele ctive etching deposition technique can be utilised to grow layered str uctures with wavelengths in the nanometer range. The microstructure in the electrodeposited Co-W alloys varied as a function of increasing W content, from crystalline Co over Co3W and Co7W6 to nanocrystalline C o. as determined by XRD. (C) 1998 Elsevier Science S,A.