Interactions between materials, environment and contaminant in microswitches

A significant impediment to implementing micro- and nanoswitch technology is that the small contact areas (10-4 to 102 μm2) and low forces (nano to micronewtons) render the surfaces inherently susceptible to contamination, which increases their contact resistance. In this work, we report on the formation of carbonaceous tribopolymer (TP) in microswitches under controlled environmental conditions in order to characterize its behavior. We clean switches coated by Pt or RuO2 thin films using vacuum bakeouts, and test them in the same chamber in ultra-high purity gases including nitrogen and oxygen. We introduce controlled levels of benzene contaminant from 0.02 to 2500 parts per million to test the immunity of different material/environment combinations to TP buildup. We find that repetitively making and breaking contact and passing electrical current through it produces TP. TP also builds up more quickly in nitrogen rather than nitrogen:oxygen backgrounds both for Pt and RuO2 materials. It appears possible to convert TP into a more conductive form, which we associate using Raman spectroscopy with an increase in its graphitic content.