Multifractal properties of Pyrex and silicon surfaces blasted with sharp particles

The blasting of brittle materials with sharp particles is an important fabrication technology in many industrial processes. In particular, for microsystems, it allows the production of devices with feature sizes down to few tens of microns. An important parameter of this process is the surface roughness of post-blasted surfaces. In this work the scaling properties of Pyrex glass and silicon surfaces after bombardment with alumina particles are investigated. The targets were bombarded at normal incidence using alumina particles with two different average sizes, 29 µm and 9 µm. This investigation indicates that the resulting surfaces are multifractal. Applying multifractal detrended fluctuation analysis (MFDFA) allowed us to determine the singularity spectrum of the surfaces. This spectrum did not depend on the target material or on the size of the particles. Several parameters quantifying relevant quantities were determined. It was found that long range correlations are responsible for the observed multifractal behaviour