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Nanoscale surface modification studied by reflection anisotropy spectroscopyLane, Paul David January 2009 (has links)
The development and control of nanoscale properties is a major goal in science and technology; for the development of such technologies it is important that there are experimental techniques which allow the monitoring of development processes in real time and in a range of environments. With this in mind much effort has been invested in the development of surface sensitive optical probes. One such technique, reflection anisotropy spectroscopy (RAS), has been applied successfully to a number of different problems since its development in the mid 1980’s. RAS as a surface specific technique is very sensitive to small changes to surface morphology, electronic structure and molecular orientation. This makes RAS a useful technique to study nanoscale changes occurring at surfaces and it is applied here to three such systems, in an attempt to develop a better understanding of both the systems and the technique. Surface defects arising from thermal processing and etching of the sample are considered and are found to have a significant effect on both the electronic structure and the morphology of the surface. The time and temperature dependences of the RAS signatures allow the monitoring of surface dynamic processes. The deposition of a monolayer of adsorbate molecules onto the surface allows a new interface to be created. Monitoring the evolution of this surface during deposition provides information about both the substrate surface and the adsorba te covered surface; a theoretical framework has been outlined to show how the sources of anisotropy from multiple thin film layers combine to give a RAS signal. Azimuth dependent RAS (ADRAS) is known to provide information on surface symmetry and can be used to determine molecular orientation. There are also a number of other angles which affect the RA spectrum from a sample. A tilted molecule causes a breakdown in surface symmetry; this work shows how such an effect can be observed.
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NC-AFM high-resolution studies of the calcite(104) surface at low temperatures with and without submonolayer of CO and H2OHeggemann, Jonas 13 September 2022 (has links)
The central aim of this thesis is to give further insights into the structural properties of the calcite(104) surface and especially to unravel its surface reconstruction by clarifying the contradicting reports of the (2 × 1) and row-pairing reconstruction. Within this thesis, the pristine as well as the CO and H2O-covered calcite(104) surface is investigated for the first time with non-contact atomic force microscopy (NC-AFM) operated at 5 K. CO terminated
tips are used in the measurements to benefit from the improved contrast capabilities and detailed understanding of contrast formation with these tips.
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