Fabrication and Characterization of Dielectric and Metallic Structures with Scanning Probe Techniques

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Small structures with dimensions of the order of the light wavelength are known to influence the properties of, e.g., light propagation, absorption, or emission. The capabilities of scanning probe microscopy (SPM) in these dimensions are to generate as well as to investigate such structures. A selfbuilt device will be utilized for the project. It can be operated as a scanning force microscope (AFM) with the possibility of electrostatic force detection (EFM), as a scanning tunneling microscope (STM), and also as an apertureless scanning nearfield optical microscope (NSOM). This research project is in close interaction with other projects of the research unit. In the present state, two main interests can already be noted: We intend to structure a metal film on top of a waveguide in order to generate hybrid modes between localized surface plasmons and the waveguide modes. Our aim is to detect the resulting plasmon field with a high lateral resolution. One possibility consists of measuring the rectification of the tunneling current using the scanning probe microscope as a STM. The very same information about the surface plasmon field is also accessible via the NSOM mode, detecting the light scattered at the tip. This will be conducted in close collaboration with the Projects B2 and C1. Another objective is the investigation and fabrication of ferroelectric domains at the microscopic scale. For detection of the domain structures we intend to make use of the piezo response of the sample and to measure the resulting thickness changes. With even higher lateral resolution we will measure the contrast of the surface charge with electrostatic force microscopy. To create the domain structures in ferroelectric crystals we will apply an electric field to the crystal locally with the tip of the scanning force microscope. The tip radius of only 30 nm enables to reach the necessary electric field with moderate voltages applied to the tip. The area below the tip where the electric field strength is sufficient to switch the orientation of the c-axis is very small. This allows to achieve high spatial resolution. These activities will be coordinated with those of Projects B1 and C4.