Characterization of a Gold‐Copper Composite Surface for Plated Wire Memory

Abstract

Gold electrodeposited at very low currents onto a coarse‐grained copper surface was found to enhance nondestructive read‐out (NDRO) memory performance when used as a substrate for the electrodeposition of Permalloy films. The structure of this Au layer is studied. Corrosion potential measurements are used to show that the Au covers about 0.4 of the surface when deposited on the coarse‐grain Cu to produce optimum NDRO properties but the same quantity of Au deposited on fine‐grain Cu covers ∼0.7 of the surface. The average Au thickness, grain size, lattice parameter, and coverage all show a sharp change at the same current. This current occurs just beyond the deposition current used to produce the optimum surface for NDRO memory wire. It appears to correspond to the transition from a Au island structure to a continuous film structure and is close to the point at which the Au deposition efficiency rises sharply. Scanning electron micrographs indicate the presence of Au islands at the low currents but do not have sufficient resolution to show their detailed structure.