Spatial self-organization of a nanoscale structure on the Pt(111) surface

A self-organized nanostructure has been observed on the Cr/Pt(111) system. Cr overlayers with various coverages were deposited on a Pt(111) surface. U pon annealing to different temperatures, metastable surface alloys characte ristic for a miscible metallic system have been observed. For a limited cov erage range from 1.5 to 3.0 ML and an annealing temperature of 800 K, a spa tial self-oganization takes place on the bimetallic surface, forming a high ly ordered hexagonal superstructure. The scanning tunnel microscope contras t of the superstructure is sensitive to the bias voltage, resulting in diff erent patterns: either a mosaic structure and/or a network consisting of on e-atom-wide lines. Relative to the Pt(111) surface, the superstructure has a (root 39 x root 39)R16.1 degrees unit cell with a dimension of 17.3 Angst rom. We propose that the network consists of Pt dislocation lines, and is c aused by a stress-induced reconstruction of the top Pt(111) layer. The mosa ic pattern is related to a two-dimensional array of Cr clusters containing only ten atoms. [S0163-1829(98)02547-8].