Nanoscale Surface Force Measurement

At nanoscale, surface forces often dominate or exert significant influence on contact interfaces. Adhesion and stiction in micro- and nanodevices are important technological challenges in nanotechnology and they are closely linked to our ability to control the surface forces. Yet our understanding of surface forces in nanoscale contacts is lacking, especially the interplay between surface roughness, material properties, contact geometry and the environment. Traditional means of measuring surface forces use a macrocontact with atomically flat mica surfaces and the forces measured by laser interferometry. Semiconductor and insulator materials cannot be measured by this technique. We have developed a preliminary AFM-based technique using colloidal probes capable of directly measure the surface forces at nanoscale. The difficulties are surface roughness control, force sensitivity of the cantilevers, the control of snapon, and the size of the probe tip. We have demonstrated that all these issues can be controlled to a large extent and reasonable surface forces can be measured between a probe tip and a flat surface down to a nanometer distance to the surface.