Atomic force microscope

• Subject Area: Condensed Matter Physics
• Term: Funded in 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 503206463

We apply for an automatized atomic force microscope which characterizes the surface of solids in a destruction-free manner. Typical samples are semiconductor crystals, quantum dots and 2D materials. This is a microscope, which images the surface structures of samples, laterally with nanometer and vertically with sub-nanometer resolution in real space by AFM (atomic force microscopy). To this end, a very sharp tip is brought close to the surface and its interaction force with the surface is measured. This force is evaluated by elastic deformation of a cantilever, which supports the tip. A predefined area is scanned by a line-wise movement of the tip and the storage of the height information pixel by pixel. The instrument does not touch the very surface and therefore cannot alter or destroy it, if the distance between tip and surface is regulated by a fast enough feedback loop. Whole wafers can be measured in an automatized manner if the instrument is capable of by approaching and measuring predefined areas on its own. The measured areas are automatically identified by landmarks which allow to reproducibly retrieve and thus to compare them with other experiments on the same sample. Beside the topographic information even functional images can be recorded. These can consist of mechanical and electrical properties of the structures. The AFM will characterize molecular beam epitaxy grown samples which is important for many different projects. One of them is the imaging of periodically modulated surface structures which are formed by a growth gradient and lead to a lateral positioning of self-organized quantum dots (SAQD). Material contrast imaging will help to analyze the diffusion on such surfaces which governs the nucleation of the quantum dots. In a further project, the surface of ion implanted semiconductors will be studied. By local droplet etching, quantum dots are fabricated for quantum information research which will also be visualized and analyzed by the AFM. Finally, hybrid 2D-semiconductors will be fabricated and investigated. AFM of surfaces is one the most important investigation methods of epitaxial layers. Up to now, we performed some investigations of this kind in external cooperations. However, we need a standard analysis of large areas on our wafers in order to shorten the feedback loop for the next growth process. That is why a modern and automatized AFM is absolutely necessary in our research.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Rasterkraftmikroskop
• Instrumentation Group: 5091 Rasterkraft-Mikroskope
• Applicant Institution: Ruhr-Universität Bochum
• Leader: Professor Dr. Andreas Dirk Wieck