Abstract
The aim of the present study is to investigate the electrodeposition of Co-Mo and Co-Mo-P alloys from the weakly acidic citrate bath and clarify factors influencing the deposition rate and composition of ob- taining alloys, as well as their structure. Sodium hypophosphite was used as a source of phosphorous. The deposition rates for cobalt–molybdenum coatings are sufficiently lower than that for pure cobalt. The alloys containing up to 10 at.% of Mo were electrodeposited. The deposition rate increases sufficiently when ter- nary Co-Mo-P alloys are electrodeposited. The increase in deposition rate in the presence of NaH2PO2 is more evident at lower values of pH. It is caused probably by the easier reduction of hypophosphite ion at lower pH and incorporation of P into alloy that change kinetics of the Co and Mo codeposition. Based on XRD data it is concluded that Co-Mo alloys has a structure of hexagonal Co of dominating planes {100} and {110}. At higher concentration of Mo in the alloy (9.8 at. %) the XRD peaks shift to lower angles that is caused by the increase of interplanar distance of formed lattice. The broadening of peaks for the electrode- posited Co and electrodeposited Co-Mo alloys is similar; therefore the values of grain size for mentioned metals may be close to the values obtained for pure Co, i.e. ~40 nm. For the electrodeposition in wafers the low frequency current pulse mode was chosen. The alloy having composition (in at. %) Co-9.3Mo-3.5P was electrodeposited. The filling of the recesses is reasonable, and the height of obtained posts is the same, and the surface is flat and consists on the fine crystallites.