Bringing light into the nanoworld: What can you do with an atomic force microscope on top of your synchrotron radiation sample holder?

Overview & Synopsis

This thesis had as a major objective to combine scanning probe microscopy in particular, atomic force microscopy with synchrotron light spectroscopies. The combination of these two types of spectroscopies is meant to be in-situ and in real time. Thus this thesis aimed at introducing new types of experimental techniques suitable for the investigation of nano-sized materials. The proposed new instrumentation, would provide chemical-specific contrast at unprecedented lateral resolution of up to 10-40 nanometers, thus overcoming existing limitations of the two families of spectroscopy methods and opening a wide range of research opportunities and challenges. For the purpose of combining these techniques an atomic force microscope was developed. The atomic force microscope (AFM) was developed around a quartz tuning fork crystal which was used as the sensor with which atomic forces are detected. The developed AFM was then used in several beam lines with essentially two different purposes. A first goal was to do spectroscopy, such as the measurement of an absorption edge, locally with the tip of the AFM. Such measurements were indeed done, but the lateral resolution is still dominated by the X-ray beam size rather than by the tip apex shape. The AFM tip was also used to measure Bragg peaks from crystals with sizes on the nanoometer scale. A second goal was to use the AFM as an instrument to mechanical interact with nano-sized systems while the X-ray beam was used to probe changes in the lattice parameter of the studied systems. Thus the AFM tip was used to elastically indent a SiGe crystal while diffraction was simultaneously measured. It was possible to observe shifts of the Bragg peak as a consequence of the applied pressure. The in-situ combination of AFM with synchrotron light permitted, in this way, to measure the Young modulus of a crystal at the nanoscale without any kind of adjustable parameter.