Dissolution dynamics of artificially structured materials

The anodic dissolution of an ultrathin cobalt film buried beneath a copper overlayer has been studied using voltammetry and chronoamperometry. The films were produced by sequential electrodeposition of cobalt and copper layers from a solution of 1.5 mol/L CoSO4, 0.5 mol/L H3BO3, and 0.008 mol/L CuSO4. Subsequent stripping analysis was performed in the same electrolyte. The blocking efficiency of the copper overlayer was a strong function of its thickness and the stripping potential. Furthermore, the inhibition provided by the copper overlayer was found to be quite sensitive to the thickness of the buried cobalt layer. For copper overlayers between 13 and 29 monolayer equivalents of charge (MEQ) a sharp transition in the dissolution behavior of the buried cobalt layer was observed. Namely, negligible dissolution was observed if the cobalt layer was less than 30 MEQ while almost complete dissolution occurred when the cobalt layer was thicker than 45 MEQ. These experiments provide guidance in selecting appropriate processing parameters for electrodeposition of Cu/Co multilayers and simultaneously provide a sensitive measure of the defect structure of such films. (C) 1999 The Electrochemical Society. S1099-0062(98)11-003-9. All rights reserved.