Orientational phase diagram of the stepped Au(001) surface

Abstract

We report an X-ray scattering study of the structure and morphology of a stepped Au(001) surface between room temperature and bulk melting. At high temperatures, between 1170 and 1220 K, the vicinal Au(001) surface appears rough. Below T 0 = 1170 K, there is a facetting transition: hexagonally reconstructed (001) facets appear in coexistence with unreconstructed, stepped domains. The tilt angle of the stepped domains increases with decreasing temperature, exhibiting a power-law behavior versus reduced temperature. The phase behavior of the hexagonally reconstructed domains follows that observed on nominally unstepped Au(001) surfaces. At T 1 = 992 K, there is a second facetting transition at which the stepped domains reconstruct to form a rotated and corrugated, quasi-hexagonal structure. The corrugation is threefold commensurate with the average terrace width, consistent with a 2° magic vicinal phase. The orientational phase diagram of vicinal Au(001) is deduced and found to be qualitatively similar to that of vicinal Pt(001), although with intriguing differences.