Pb ML is deposited either as UPD ML or using our new e-less approach. To improve the interlayer transport of Co during the growth, the monolayer (ML) of Pb is pre-deposited on Cu surface before the Co growth. The benefit of Pb ML presence on Co interlayer kinetics during the growth is evident by high quality of Co films obtained. They are characterized by large 2D grains having the width to height ratio in excess of 500. The ultrathin Co films are continuous, highly conformal and very smooth yielding a 2D-like appearance. The saturation roughness measured over the range of 10 x10 microns for 10 nm thick Co films is only 3 nm. The Co films show extremely soft properties and very high electrical conductivity which indicates a very small concentration of defects and high quality of the grain boundaries. The benefit and application of this Co deposition protocol is discussed through the analysis of Cu/Co GMR stacks deposited with and without assistance of the Pb ML as surfactant. The practicality of our e-less growth of Cu/Co GMR stacks is emphasized due to its simplicity, fidelity of control and low capital cost of equipment.
In conclusion, our results also re-confirm the fact that Pb surfactnat-assisted electrochemical growth could be used to produce smooth 2D films of various metal overlayers even in situations where both thermodynamics and kinetics conditions do not favor positive outcome.
The authors acknowledge the support from Lam Research Corporation and NSF Chemistry division under the contract # 0955922.
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