A novel model for the effect of geometric properties of micro/nanoscale asperities on surface adhesion

The geometric properties, size and shape of surface asperities, have an important effect on surface adhesion in micro electromechanical systems (MEMS). In this paper, the effect of geometric properties of deposited samples on the adhesion of contact area between surfaces of the samples and AFM probe tip has been studied. For this purpose four silicon surfaces were used, three of which coated and one non-coated. Two of them deposited with TiO2 and one with Au, on the Si (1 0 0) substrates. The root mean square (RMS) roughness of all four samples is less than 14 nm. The depositing was done by thermal evaporation method. The calculation of interaction forces shows that the method of deposition, types and thickness of coating films and the surface roughness have aided to increase the repulsion in the contact area between probe tip and the surface of the samples. In addition, as a result a novel model is proposed in which it is assumed that the probe movement is the sum of probe deflection due to the presence of the asperities and the presence of the repulsive forces between asperities and probe. The results are compared using the Rabinovich model.