Influence of bath composition on the electrodeposition of cobalt-molybdenum amorphous alloy thin films

Qiaoying Zhou,Hongliang Ge,Guoying Wei,and Qiong Wu College of Science,China Jiliang University,Hangzhou 310018,China

摘 要：Cobalt-molybdenum （Co-Mo） amorphous alloy thin films were deposited on copper substrates by the electrochemical method at pH 4.0. Among the experimental electrodeposition parameters,only the concentration ratio of molybdate to cobalt ions （[MoO42-]/[Co2+]） was varied to analyze its influence on the mechanism of induced cobalt-molybdenum codeposition. Voltammetry was one of the main techniques,which was used to examine the voltammetric response,revealing that cobalt-molybdenum codeposi-tion depended on the nature of the species in solution. To correlate the type of the film to the electrochemical response,various co-balt-molybdenum alloy thin films obtained from different [MoO42-]/[Co2+] solutions were tested. Crack-free homogeneous films could be easily obtained from the low molybdate concentrations （[MoO42-]/[Co2+]≈0.05） applying low deposition potentials. Moreover,the content of molybdenum up to 30wt% could be obtained from high molybdate concentration; in this case,the films showed cracks. The formation of these cracked films could be predicted from the observed distortions in the curves of electric cur-rent-time （j-t） deposition transients. The films with amorphous structure were obtained. The hysteresis loops suggested that the easily magnetized axis was parallel to the surface of the films. A saturation magnetization of 137 emu·g-1 and a coercivity of 87 Oe of the film were obtained when the deposition potential was -1025mV,and [ MoO42-]/[Co2+] was 0.05 in solution,which exhibited a nicer soft-magnetic response.

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