Friction and pull-off force on silicon surface modified by FIB

The friction and adhesion forces were measured for silicon surfaces that had various patterns having cyclic asperity. The patterns were created by using a focused ion beam (FIB) to mill ditches and to deposit platinum mounds. To study the effect of cyclic asperity on the forces, the friction and pull-off forces were measured between the pattern and a flat, square scanning probe (0.7×0.7 μm² ) of an atomic force microscope (AFM). Both the friction and pull-off forces decreased as the asperity increased (i.e., as the ditch depth or mound height increased). The decrease was greater for the cyclic ditches than for the cyclic mounds. The friction force was proportional to the pull-off force, which indicates the importance of reducing the adhesion force when devising lubrication methods for micromachines and micro-electro mechanical systems (MEMS)