Direct atomic imaging of solid surfaces. II. Gold (111) surfaces during and after in situ carbon etching

High resolution electron micrographs are presented which show the atomic structure of gold (111) surfaces during and after electron-beam-induced etching of surface carbon contaminants by water vapour. Initial carbon removal leaves a persistent electron-beam-resistant layer on the surface which is believed to be molecular benzene with a Van der Waals spacing of 7.3 Å. During this removal process and later cleaning, elastic deformations of the gold indicated by large, normal surface expansions (typically ∼10%) and the development of a pronounced "hill and valley" morphology are observed. Accommodation of these elastic deformations by surface dislocations is also observed. These point to an in-plane expansion on the gold (111) surface which is estimated at 5%. Finally, the results are related to a recent solid state model for gold surfaces, experimental observations on multiply twinned particles and stacking faults in small gold particles, and the occurrence of benzene is linked to the mechanism of the etching process.