Effect of relative vapor pressure on separation of nanoscale contact in atomic force microscope

Abstract

The separation of nanoscale contact junction is investigated in an atomic force microscope at various relative vapor pressure conditions. Gradual increase in adhesion force is observed as the relative vapor pressure increases. However, the force-deformation behaviors of the water-mediated nanoscale contacts vary extensively with the relative vapor pressure conditions. At low relative vapor pressure (p/ps<0.06), water molecules play a role as a weak glue contributing solid extension. In contrast, at high relative vapor pressure (p/ps=0.8), the highest adhesion force is observed without indication of the solid extension. The meniscus collapses and forms a water column after solids separates at an intermediate relative vapor pressure condition (p/ps=0.4). The detailed analysis revealed the transition of adhesion mechanism from the solid-dominant adhesion to liquid-dominant adhesion as the relative vapor pressure increases.