Electrodeposition of copper in the presence of an acoustically excited gas bubble

Copper has been electrodeposited in the presence of an acoustically excited gas bubble (Ar bubbles with radii similar to 1.5 mm held below a copper plate). Under the conditions employed, an acoustic pressure amplitude of 69.5 Pa is sufficient to excite multiple surface wave modes on the bubble wall. This is observed using high-speed imaging. This oscillation generates significant micromixing, which brings fresh electrolyte to the electrode surface leading to an enhanced deposition current. Scanning electron microscopy reveals radial streaming patterns in the resulting copper deposit. Experiments carried out using a lower acoustic pressure amplitude of 50.5 Pa (such that only the Faraday wave is excited) exhibit a lesser degree of streaming and mass transfer enhancement. No significant spatially averaged current enhancement is seen if the bubble is only undergoing breathing mode oscillation. (c) 2007 Elsevier B.V. All rights reserved.