Vapor-Deposited Gold Electrodes: Effects of Undercoatings

Abstract

Vapor-deposited metal-film electrodes on smooth glass substrates are attractive for optical reflectance studies of electrochemical systems because of the high optical quality of the surface and a ratio of true to apparent area relatively close to unity. With gold, the double layer capacity of the vapor-deposited films has been found by the authors to be approximately one-half that observed on mechanically polished electrodes of the bulk metal at the same potentials. Metals such as gold, however, do not adhere well when deposited directly on a glass substrate, and some kind of undercoating generally has been used by various authors in order to obtain adherence, e.g., Paik et aI. used glass Ta-Pt-Au. A number of substances yield adherent vapor-deposited gold films. The purpose of this note is to call attention to the fact that these undercoats can seriously interfere with optical and electrochemical measurements.