Preparation of a stable atomic force microscope tip for reproducible local work-function measurements by scanning electrostatic force microscopy

Kazuto Yagi and Masamichi Fujihira

Department of Biomolecular Engineering, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8501, Japan

Reproducibility of local work function measurements was examined by scanning Maxwell stress microscopy with various types of gold-coated atomic force microscope (AFM) tips such as those i) as received, ii) cleaned with ozone, iii) cleaned, then reduced with ethanol, and iv) chemically modified with 1-decanethiol after the cleaning, the reduction, and gold sputtering. The sample was a 1-decanethiol coated Au(111) surface which was prepared by gold-vacuum-vapor deposition on mica at ca. 300 oC. The first three types of the AFM tips exhibited gradual change and scatter in observed contact potential differences (CPDs) with the Au(111) surface covered with a self-assembled monolayer of 1-decanethiol, while the last modified tips with 1-decanethiol gave the stable and reproducible CPDs.