Scanning force microscope Z-calibration using steps on chemically etched mica

Abstract

Obtaining reliable dimensional information in all three directions is very important in scanning force microscopy (SFM). Calibration standards for SFM should be easy to produce and reliable. For example, mica is often used as a lateral calibration standard, because lattice fringes are relatively easy to obtain. However, reliable height information is hard to get. Pits formed by lithography (180 nm in depth) are used for vertical calibration by some SFM manufacturers.1 These standards have 10variability and are large on the size scale of monolayers. Colloidal gold particles have been proposed as one kind of SFM vertical standard, but the size variability of these particles (e.g. ranging from 5 to 24 nm) makes their use of limited practical value.One solution to the problem is to use chemically etched mica as height calibration standard. Mica has a layered structure, and its c-axis is well denned and weakly bonded. In this study, we used muscovite mica which has c-axis lattice spacing of 10 Å.