Nanotribology of behenic acid monolayer and its aggregation state

The tribological properties of behenic acid monolayers in CS and L2 phases were investigated on the basis of scanning probe microscopic observations. The lateral (friction) force of the monolayers in CS and L2 phases increased consistently with applied force. The increment in CS phase comes from an increase in contact area between a probe and the monolayer owing to elastic deformation, while that in L2 phase does from not only increase in contact area owing to plastic deformation but wear of the monolayer. The lateral force of the monolayer in CS phase was independent of the scan velocity. On the other hand, the monolayer in L2 phase exhibited the scan velocity dependence of the lateral force. The difference in tribological properties of the monolayer is attributable to the static mechanical properties of elasticity and plasticity which are governed by the molecular packing in monolayer.