Scanning Force Microscope

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With this proposal, funds are requested for the acquisition of a scanning force microscope (AFM, atomic force microscope). The instrument shall be used for recording materials contrasts, especially for soft samples as well as for the study and local modification of electrode surfaces in solution. Scanning force microscopy exploits forces between a microscopic tip and the sample. The tip is located at the end of a cantilever with a size in the micrometer range. The forces cause a deflection of the cantilever which is measured by a laser beam reflected from the backside of the cantilever onto a split photodiode. A mechanical actuator scans the tip sequentially to different locations of the sample. During this process, a control variable, e.g., the deflection, is kept constant by an electronic feedback loop. The stored values of the required vertical adjustment of the tip position can be transformed to a false-color image. The opportunities of the method are significantly enhanced, when a complete force-distance curve is stored at each location, other quantities measured besides deflection and modified tip are used that allow conclusion on local mechanical, electrical and electrochemical properties of the sample.The instrument to be acquired will be used to study self-assembly processes or organic molecules at surface. Such layers play an important role for the generation of experimental models of biological membranes, with which essential processes can be studied under well-defined conditions outside biological organisms. Furthermore, electrochemically switchable functional layers shall be studied with respect to film formation processes and their electrical and electrochemical properties. The new instrument will also be used to understand the formation of oxide layers in corrosion processes and the evolution of interphases within batteries. The versatile capabilities of the instrument will also be employed for the characterization of the surfaces of complex nanoparticles in contact with layered oxide materials for catalysis and energy storage. For this purpose, it is important to switch the state of the sample during the imaging process. The tip of the instrument shall not only be used as measurement probe but also as a tool for local surface modification in the nanometer size regime. Hollow cantilevers can for instance be used for the local delivery of reagent solutions for the electrodeposition of metal structures. Another approach aims for the modification of the tips to obtain nanometer-sized plasmonic light emitters for local spectroscopy.