Field Ion Microscopy and Mass Spectroscopy of Sulfur Covered Silver Surfaces

Abstract

__ _ _ _~~it is t r a n h r m c d into a bulk xilver sulride. Multilayer adw'ption of sulfur can be assumed as a precursor statc during and after exposure at low temperature. During exposure a t room temperature or during heating t h e low temperature state t o room temperature the physisorbed sulfur layer is responsible for the supply or sulfur. The changes in the FEM pattern on heating above 453 K are induced by the transport of silver ions. A chemisorbed slate seems to be stable after the decomposition of Ag2S abovc 723 K. These observations differ from those on Pt a n d W but are in agreement with the generally observed higher reactivity of silver towards sulfur. Helpful discussions Hith Dr. D. Cocke, Mr. 0. Frank and Dr. W. A. Schmidt and finaiicial support by the Deutsche Forschungsgemeinschaft and the Scnat fur Wirtschaft of West-Berlin (ERP-Fonds) are gratefully acknowledged. K. Hayek expresses his appreciation for a fcllouship of the Max-Planck-Gesellschaft.

Surface Reactions on an Atomic Scale

“…This is a consequence of field adsorption of methanol. The high intensity of Cu + -ions at unusually low electric fields may be connected with a particular ion formation process, which has been observed earlier (22,23). If an ionic surface compound (Ag 2 S or Cu 2 0) is present as a dielectric layer on top of the metal emitter, ion transport can be achieved by the field, and field evaporation can be observed at unusually low fields.…”

“…This finding suggests that dissociation of adsorbed CO takes place and is promoted by the presence of steady (positive) electrical fields. Shincho et al, (23), report the dissociative adsorption of CO at step sites on a macroscopic Ru{l,l,10) surface. Our measurements confirm this result, however, the concentration of carbidic and oxidic species is small here because the high frequency pulses (f=100 Hz, i.e.…”