Electrochemical Quartz Crystal Microbalance Study of Additive Effects in Pulsed Deposition of Cu-Co Alloys

Abstract

Additives have strong effects on the physical properties of electrodeposited alloys that are used in data storage applications. 1 The electrochemical quartz crystal microbalance (EQCM) has been employed to study the effect of additives during electrodeposition, 2,3 corrosion, 4,5 and battery electrode processes. 6 Buttry and Ward reviewed the technique thoroughly. 7 Pulse-plating applications of the EQCM have principally focused on internal stress measurements in multilayered alloys exhibiting giant magnetoresistance. 8,9 Since electrolytes used in producing such multilayered alloys contain the more noble metal ion usually in small concentration, 10 well-defined hydrodynamics are important for electrochemical investigations of these systems.In a previous study, the additives saccharin and sodium dodecyl sulfate (SDS, also known as sodium lauryl sulfate) had a significant effect upon the composition, morphology, and microstructure of pulse-plated Cu-Co alloys. 11 In this study, a rotating EQCM 12 (r-EQCM) is used for the first time to study how additives affect fundamental deposition and corrosion processes that govern the composition and morphology of pulse-plated alloys under controlled hydrodynamic conditions. The r-EQCM is particularly well-suited for this problem, since it allows one to monitor deposition rates in situ for the pulse on-and off-times separately with well-defined fluid flow. Pulse-plating studies of alloys employing additives are available (Ref. 13-15 and references therein), but relatively few of them deal specifically with the transient behavior during pulsed deposition. 16,17 This problem is of practical interest however, since pulse-plating with additives could prove especially useful as certain metallization processes become more demanding. 18 ExperimentalA rotating electrochemical quartz crystal microbalance described in detail elsewhere 12 was employed using AT-cut quartz crystals (nominal resonance frequency 10 MHz) with Au electrodes. The working electrode (WE) area was 0.203 cm 2 . A Zahner potentiostat (model IM6, Germany) controlled the pulsed deposition while a PC acquired data at a frequency of 50 Hz unless noted otherwise. A mercury/mercurous sulfate electrode (MSE) acted as the reference electrode (Radiometer, France), while a Pt coil served as the counter electrode. Approximately 100 nm of Cu was deposited on the WE from the electrolyte at 2 mA/cm 2 and 1000 rpm before starting pulse experiments; direct deposition on Au gave similar results, but the reproducibility was not as good. Five pulse cycles were measured after 25 prior pulse cycles. This was found to be necessary to approach steady-state conditions. The duty cycle (the ratio of the pulse on time to the pulse period) was 20%, and the pulse period was 2 s unless noted otherwise. The off-time current density i off for all experiments was zero, while the on-time current densities i on , listed in Table I, were chosen to give an alloy composition Cu ϭ 0.5 for short pulse periods (this is discussed in more detail below). 19 ...

A study of the electrodeposition of Co–Cu alloys thin films on FTO substrate

“…However, the electrodeposition made the Co-Cu alloy in nonequilibrium supersaturated solid solution state. It is well known that the nucleation-growth process, the morphology, the microstructures, and magnetic properties of Co-Cu electrodeposits depend greatly on solution composition, pH, temperature, and current density or applied potential [11][12][13][14][15][16]. Several baths with different compositions have been used for electrodeposition of CoCu thin films.…”

Effect of pulse plating and additive on phase separation in Cu–Co nano-granular alloys

“…A few attempts have been made for the PC electrolysis of Cu-Co alloys [11,[27][28][29], even though the latter has been considered as a better option for making various types of nanocrystalline films [30][31][32]. Kelly and co-workers [11,27,28] have studied the effect of additives like sodium dodecylsulphate (SDS) and saccharin during the pulse electrodeposition of Cu-Co alloys. They found that SDS enhances Co displacement by Cu while saccharin impedes this process during open circuit conditions.…”

Nanostructured Materials Synthesized Using Electrochemical Techniques

“…With regards to the Cu-Co multilayers nanostructures, Kelly et al [265,266] have clearly shown that sodium dodecyl sulfate promotes the displacement reaction of Co by Cu 2þ during pulse off-times. Gundel et al [267] assumed that the displacement reaction could be negligible under galvanostatic conditions.…”