FIELD ION MICROSCOPE STUDIES OF SURFACE RECONSTRUCTIONS

Abstract
The reconstruction of various metal surfaces has been investigated in atomic detail with the field ion microscope. Unreconstructed (bulk-terminated) surfaces were produced by low-temperature field evaporation and induced to reconstruct either by heating alone or heating in the presence of deuterium. Field ion microscope images recorded before and after the field-free heating interval were used to determine the temperature at which restructuring takes place and the structure of the reconstructed surface. The results clearly showed that the (110) planes of Pt and Ir reconstruct to missing-row structures. The temperature required for restructuring was approximately 300 K for Pt and 500 K for Ir. The reconstructions were observed for (110) planes as large as 40-50 Å diameter and for clusters as small as five atoms. The direct observation of missing-row structures for these small clusters provides convincing evidence that the reconstructions are driven by short-ranged atomic interactions. Missing-row structures were also produced on higher index planes of Pt such as (311), (211), and (511) by heating to temperatures above 400 K. Small clusters of atoms on the (110) plane of Ni did not reconstruct thermally, but did reconstruct to a missing-row structure when heated to 150-170 K in the presence of 10^-8 Torr deuterium.