POTENTIAL-INDUCED STRESS IN THE SOLID-LIQUID INTERFACE - AU(111) AND AU(100) IN AN HCLO4 ELECTROLYTE

The cantilever bending method is applied to the determination of the p otential-induced interface stress for Au(111) and Au(100) in 0.1M HClO 4. The bending of the crystal plates was observed using an electrochem ical STM. By a reconsideration of the elasticity theory of bending, it is shown that the entire interface including the liquid part contribu tes to the measured stress. The potential-induced lifting of the recon struction of the two surfaces was observed using the STM simultaneousl y with the measurement of the interface stress. By making use of the f act that after cycling the potential between - 140 and 960 mV versus S CE the surfaces remain in an unreconstructed state, one can determine independently the stresses which are associated with the surface recon struction and with the specific adsorption of ClO4- ions. The stress i nduced by the specific adsorption is comparable in size to the adsorpt ion-induced stress for surfaces in vacuum. The reconstruction-related changes in the surface stress are discusssed in the context of theoret ical models for the reconstruction. The results support the notion tha t the stress is the driving force for the reconstruction on Au(111), w hereas on Au(100) stress relaxation associated with the reconstruction is not a sufficient source of energy to force the surface into the re constructed state. (C) 1997 Elsevier Science B.V.