Preparation, comparison and performance of hydrophobic AFM tips

Hydrophobic coatings for atomic force microscopy (AFM) tips generated throu gh sputter coating with gold, chemical vapour deposition from a hexafluorop ropene plasma or silanization with octadecyltrichlorosilane are compared wi th respect to their macroscopic hydropobicity, influence on tip radius, abr asion behaviour during imaging and complexity of the coating procedure. The performance of the coated tips is assessed by measuring their adhesion fro m force curves at different humidities. From these tests, the hexafluoropro pene plasma-treated tips turned out to exhibit the best overall quality and so are used to image the hexagonally packed intermediate surface (HPI) lay er of the eubacterium Deinococcus Padiodurans, a natural two-dimensional pr otein crystal, to demonstrate the capability of these tips to image fragile , hydrophilic samples at high humidities with reduced tip-sample adhesion. Copyright (C) 1999 John Wiley & Sons, Ltd.