Electrochemical Pretreatment of Thin Film Platinum Electrodes

Abstract

Thin film noble metal electrodes and electrode arrays prepared by photolithographic process suffer from contamination of the surface by the traces of transition metals and their oxides which are used as adhesion promoters at the insulating substrates. This contamination is an ongoing process as the transition metals migrate continuously along the grain boundaries through the thin (1000–4000Å) layer of the noble metal. The transition metal oxide affects the electrochemical properties of the noble metal surface and also its electron work function. A simple electrochemical pretreatment has been developed which removes these contaminants from the surface and “anneals” the surface in such a way that acceptable electrochemical behavior identical with a thick noble metal electrode is obtained. It consists of electrochemical etching of the surface by pulsing it between 0 and +2V in solution containing 0.08M EDTA, 5.2% , and for 5–10 min. It is then followed by cycling of the applied potential between 0.4 and −0.4V in for 10 min. Surfaces prepared by this procedure have remained clean for a period of at least 24h.