Thesis defense of Stefanie Hilgers

This work focuses on the detailed structural and chemical characterization of Sb nanoribbons on the Ag(110) surface. For this purpose, surface-sensitive methods, such as low-energy electron diffraction (LEED) and scanning tunneling microscopy (STM), are used to determine the structural arrangement of the nanoribbons. X-ray photoelectron spectroscopy (XPS) is utilized to characterize the various bonding environments. The combination of these measurement methods enables the construction of a structural model of the Sb nanoribbons on the Ag(110) surface.

For a coverage of 0.5ML a c(2x2)-reconstruction is observed. By LEED-IV analysis and XPS measurements, this reconstruction can be identified as a substitutional alloy. XPS measurements show a distinct alloy component in both the Sb 4d signal and the Ag 3d signal, which can be attributed to the bond between Sb and Ag.

For higher coverages, the formation of Sb nanoribbons is observed in STM. In this work, the Ribbons I and Ribbons II phases, with coverages of 1ML and 1.24ML, are examined in detail. As the coverage increases, the alloy component decreases in the XPS measurements, suggesting a dealloying process and the growth of Sb ribbons directly on the Ag(110) surface. In addition, based on angle-resolved measurements at Theta = 0° and Theta = 60°, a two-layered growth of the ribbons can be identified.

In the STM data, narrow and wide nanoribbons are identified, consisting of two or four atoms in the topmost atomic layer, respectively. The nanoribbons are arranged stochastically on the surface, which is reflected in the LEED pattern as a spot splitting along the [1-10] direction. This splitting is directly linked to the ratio of narrow to wide ribbons. For the Ribbons II phase, additional spots are visible in LEED along the [001] direction. Following the LEED analysis, these spots are attributed to a faceted surface structure, likely arising from a lattice mismatch between Sb and Ag, leading to a tilt of the Sb nanoribbons.

Based on these results, the previously proposed structural model, according to which the Sb nanoribbons grow in a single layer on top of the alloy, can be refuted. Instead, a new structural model is presented, consisting of two‑layered Sb ribbons that grow in the gamma-Sb structure directly on the Ag(110) surface.