Direct visualization of the dynamic behavior of a water meniscus by scanning electron microscopy

Scanning probe microscopic imaging can be complicated by the capillary forc e of a water meniscus formed in air between the tip and the sample. Water m enisci between a tungsten tip and Pt/C-coated mica and their dynamic behavi or have been directly visualized by environmental scanning electron microsc opy. Rapid scan secondary electron micrographs give information in the 100 nm range. We found that static models are not appropriate to describe the s hape of a meniscus when the tip is moving across the sample. The surface st ructure and its properties influence the affinity of the meniscus thus caus ing a varying capillary force that may exhibit a vertical and a lateral com ponent as well. Our experimental data indicate that the Kelvin equation als o holds for microscopically small water menisci. (C) 1998 American Institut e of Physics. [S0021-8979(98)04221-2].