Berlin 2012 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 15: Poster: New Instruments and Methods

CPP 15.4: Poster

Dienstag, 27. März 2012, 18:15–20:15, Poster A

Characterization of AFM tips using graphite steps — •Friedrich Lüders, Ann-Kristin Löhmann, and Thomas Thurn-Albrecht — Institut für Physik, Martin-Luther-Universität Halle-Wittenberg, Germany

To investigate the morphology and mechanical characteristics of soft polymer samples on the nanometer scale, Atomic Force Microscopy (AFM) in Intermittent Contact Mode (ICM) is a commonly used technique. The AFM image is always a convolution of the surface topography and the shape of the tip. The resolution of an image is therefore limited by the sharpness of the tip. Also in ICM the tip indents into the sample, into softer areas more than in harder regions. For a quantitative analysis of AFM images the exact shape of the tip must be known.

We present a simple method for characterization of an AFM tip by scanning the steps between different layers (0.355 nm high) on a graphite surface. These atomic steps provide a much higher aspect ratio than standard AFM tips (radius 5-10nm) and hence can be used for the tip characterization. The image of a graphite step contains information about the shape of the lowest few nanometers of the tip. The width of the imaged step can be used as a measure for the resolution.

To test the results of the calibration method, a sample of hexacontane on graphite was used. As expected the lamellar structure of the sample with a periodicity of 7.5 nm could be imaged with sharp tips while with the blunter tips imaging of the lamellae was impossible.