Frictional properties of antimony nanoparticles: The influence of contact area, structure, and surface contamination

We performed experiments where the frictional resistance of antimony nanoparticles with varying contact areas is measured in ambient conditions as well as in ultrahigh vacuum while they are pushed by the tip of an atomic force microscope (AFM). Two different procedures have been used in independent studies to investigate the frictional properties of these particles during dislocation using the AFM operated in the contact mode or dynamic (tapping) mode, respectively. Both experimental approaches revealed a linear dependence of the frictional properties on contact area. Moreover, both methods detect a sudden and distinct increase in frictional resistance at around 15000 nm(2) particle size, which coincides with a structural transition of the particles from an amorphous to a crystalline core state and confirms our earlier data showing the same result. Possible reasons for this effect are discussed in terms of both the atomic structure of the antimony particles as well as the interface structure. Some of the observed frictional behaviour of the particles may be explained considering the influence of sample contamination.