Stylus contact on short wavelength random surfaces: a simulation study

Abstract

Stylus scanning remains a crucial method in surface micro- and nano-topography measurement. Its accuracy, especially at shorter wavelengths, depends on the relation of the stylus geometry to surface parameters. We present a 3D computer simulation of measuring non-Gaussian random surfaces with arbitrary tip shapes, studying both the surface distortion and the stylus contact distribution. After a brief discussion of the surface generation and geometrical contact algorithms, this paper concentrates on examples of symmetrical styli having characteristic sizes not much smaller than the surface correlation lengths. It thus attempts to examine the breakdown region as we seek to measure finer topographies. The measuring error appears to be generally smaller with a three-pyramid stylus than with other styli as limits are approached. Perhaps counter-intuitively, the errors in common parameters on surfaces of a similar correlation length and roughness amplitude can be smaller when their kurtosis is high, a condition that might become more common with deliberately imposed nanostructuring.