Experimental studies on relationships between the electron work function, adhesion, and friction for 3d transition metals

Experimental studies on the relationships between the electron work function (EWF), adhesion and friction for 3d transition metals were reported. EWF was measured using a scanning Kelvin probe. Adhesion and friction under light loads between a silicon nitride tip and sample surfaces were evaluated employing an atomic force microscope (AFM) that may also function as a lateral force microscope (LFM). Friction of the samples under a sharp tip at higher load levels was also measured using a microtribometer. It was demonstrated that there was strong correlation between the EWF, adhesion and friction. Higher EWF corresponded to lower adhesive force and thus to lower friction when measured under light loads using the AFM/LFM. Such a correlation stems from the fact that the measured adhesion and friction are largely attributed to the intrinsic interaction between the sample and AFM/LFM tip, which is governed by the electronic behavior reflected by the EWF. However, such a correlation became weaker when the friction was evaluated under a sharp tip at higher load levels. In this case, the friction behavior of a target metal was mainly determined by its mechanical behavior. (C) 2004 American Institute of Physics.