Berlin 2005 – wissenschaftliches Programm

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O: Oberflächenphysik

O 15: Postersitzung (Adsorption an Oberfl
ächen, Epitaxie und Wachstum, Organische Dünnschichten, Oxide und Isolatoren, Rastersondentechniken, Zeitaufgelöste Spektroskopie, Methoden)

O 15.61: Poster

Freitag, 4. März 2005, 17:00–20:00, Poster TU D

Accuracy and Resolution Limits of Kelvin Probe Force Microscopy — •Christian Loppacher, Ulrich Zerweck, Tobias Otto, Stefan Grafström, and Lukas Eng — Institut für Angewandte Photophysik, Technische Universität Dresden, D-01062 Dresden

Kelvin probe force microscopy is a scanning probe technique capable of mapping the local surface potential or workfunction on various surfaces with high spatial resolution. This technique can be realized on the basis of either an amplitude-sensitive method or a frequency modulation method, which are sensitive to the electrostatic force and its gradient, respectively. We present a detailed experimental and theoretical study of the accuracy and resolution provided by the two methods, including a novel setup for the frequency modulation technique. Au(111) with a submonolayer coverage of KCl serves as a test sample exhibiting extended sharply bounded areas that differ in workfunction by an amount well known from ultraviolet photoelectron spectroscopy. The experimental results are compared with the predictions of a numerical simulation based on a realistic model for the tip-sample geometry. Good agreement is found. The experimental analysis allows us to specify the lateral, vertical and potential resolution that can be achieved with the two methods for a given tip size. Our work clearly proves that the frequency modulation method is preferable in most applications because it (i) provides much higher lateral resolution, (ii) yields quantitative surface potential values on areas larger than the tip radius, and (iii) is little affected by variations of the tip-sample distance during topographic imaging.