Electrodeposition of copper in an alternating electric field

Nicholas LeCompte, Prof. Daniel Lathrop

Process – DC Electrodeposition●Electrocell: two copper electrodes in a cupric sulfate solution

●Cu – 2e- → Cu 2+ oxidation at the anode, ion released

●ions flow across electrocell under electric field governed by Laplace equation, with on the cathode

●Cu 2+ + 2e- → Cu reduction at the cathode, sticks to electrode

Mullins-Sekerka instability causes growth to become nonuniform and ramified

∇2V≈0

V=V 0

Motivation – AC ElectrodepositionScientific:

● First (to our knowledge) direct experimental study of Laplacian pattern formation with non-constant boundary condition● Study of AC-biased electrochemistry

Applications:

● Electroplating shown to be smoother under AC field conditions● Formation of nanoscale electronics

Figure taken from J. Xu, K. Wang, Y. Xu 2007. Chemistry Letters 36 868

Procedure

2D experiments

3D experiments

VAC VDC 2.0 4.0 3.0 3.0 5.0 2.5 6.0 2.0

VAC = 5.0VVDC = 5.0V

Prediction:

δ= Dc

f

Results

Results

●δ ~ f -0.12± 0. 04

●Poor agreement with expectation

● However, we still showed monotonic decrease in length scale w / increasing frequency

●Possible explanation of increasing uniformity on phase diagram

For more information, please visit my poster.

Acknowledgements

Thanks to:

●Doug Kelley, Daniel Lathrop, Don Martin, Matt Paoletti, Santiago Triana, Daniel Zimmerman, and the rest of Lathrop Lab for their technical assistance, valuable discussions, amusing lunches, and the cowbell

● the FabLab for their friendliness and donation of deionized water