An implantable electrode and method for manufacturing the electrode wherein the electrode has a strong, adherent surface inert coating on a conductive coating on the electrode surface, which demonstrates an increase in surface area of at least five times when compared to smooth platinum of the same geometry. An iridium oxide coating may be formed on a platinum coating by a physical deposition process, such as sputtering. The process of electroplating the iridium oxide surface coating is accomplished by voltage control processes. A gradient coating of iridium oxide ranging in composition from essentially pure platinum to essentially pure iridium oxide is produced by sputtering.