RTM Untersuchungen an zweidimensionalen Nanostrukturen am Beispiel der reinen Au(100)-Oberfläche und des selbstassemblierten Systems Sauerstoff auf Cu(110)

In this STM study, nanostructures on metallic single crystals are observed under UHV conditions. The aim of the work at the Au(100)-surface is to evaluate an energetic quantity, namely the step free energy, from a topographic structure information. Adatom and vacancy islands are produced on the tempered reconstructed Au(100)-surface by evaporation of submonolayer quantities of gold and sputtering with Argon ions, respectively. As noted before, these islands have a rectangular shape with the long side oriented along the parallel reconstruction lines. The initial (aspect) ratio of the long to the short side is about 10. The decay of these islands is correlated with a decrease of the aspect ratio to approximately 1. After that the aspect ratio varies merely stochastically around this mean value. We could observe adatom islands at T = 353 K, which neither grow nor decay over a long period of time and whose aspect ratio varies stochastically around the mean value of 1. In conclusion, we assume that these islands are in a thermodynamic equilibrium situation or at least close to it. By averaging over these island shapes, we obtain the equilibrium shape for this temperature. From island shape fluctuations we make a quantitative determination of the mean step free energy to 170 meV per atom. In completely separated experiments from the described ones above, the formation of the so-called (2x1) oxygen stripe phase on Cu(110) is imaged in situ, and simultaneously a quantitative determination of the induced surface stress is accomplished. The bending bar technique is utilized with the bending measured by the STM. Due to the anisotropy of the Cu(110) surface, two experiments, one with the [1(-1)0]- and a second one with the [001]-direction along the bar have to be carried out for a quantitative analysis of the induced surface stress. From the two experiments we calculate the induced stresses in both directions. We find that the difference of the surface stresses of the (2x1)O phase on Cu(110) and the clean Cu(110) surface is compressive for both directions, in accordance with the adsorption of oxygen on other surfaces. The stress depends significantly on the coverage. The data can be fitted with an exponential function. Furthermore the fit for the stress difference orthogonal to the stripes is used for a quantitative analysis of the periodicity of the oxygen stripes.

Grantor dc:publisher

Publikationsserver der RWTH Aachen University

Year dc:date

2004

Author dc:creator

• Bombis, Christian

Contributors dc:contributor

• Ibach, Harald

• info:eu-repo/classification/ddc/530
• Gold
• Kristallfläche
• Nanostruktur
• Rastertunnelmikroskopie
• Kupfer
• Adsorption
• Sauerstoff
• Physik
• RTM
• Au(100)
• Cu(110)
• Stufenenergie
• Oberflächenspannung

Statement dc:rights

• info:eu-repo/semantics/openAccess

Language dc:language

ger

Identifier

https://publications.rwth-aachen.de/search?p=id:%22RWTH-CONV-123649%22

OAI identifier oai:identifier

oai:publications.rwth-aachen.de:62051