Ageing of a Microscopic Sliding Gold Contact at Low Temperatures

Abstract

Nanometer-scale friction measurements on a Au(111) surface have been performed at temperatures between 30 and 300 K by means of atomic force microscopy. Stable stick slip with atomic periodicity is observed at all temperatures, showing only weak dependence on temperature between 300 and 170 K. Below 170 K, friction increases with time and a distortion of the stick-slip characteristic is observed. Low friction and periodic stick slip can be reestablished by pulling the tip out of contact and subsequently restoring the contact. A comparison with molecular dynamics simulations indicates that plastic deformation within a growing gold junction leads to the observed frictional behavior at low temperatures. The regular stick slip with atomic periodicity observed at room temperature is the result of a dynamic equilibrium shape of the contact, as microscopic wear damage is observed to heal in the sliding contact.

Chemical effects on the sliding friction of Ag and Au(111)

“…In Ref. [6], Gosvami et al investigated the ageing of single-asperity sliding contacts between an AFM-tip and an Au(111) surface at low temperature and under UHV conditions. There the authors also observed stable stick-slip with atomic periodicity.…”

“…In contrast to single-asperity friction measurements performed in ultra-high vacuum (UHV)-conditions in Refs. [5,6], the authors reported on 2 / 3 n F -dependence of the friction force on gold nanoparticles measured in ambient conditions, where F n is the normal force [8]. In Ref.…”

“…The growth of thin metallic films onto silicon devices for operation in reciproc motion appears to be a feasible alternative. Recently, the nanoscale friction and wear behavior of metals has been investigated [5][6][7][8][9][10]. In the low load regime where adhesive force prevails, friction has been reported to vanish and the sliding of a slingle asperity onto single crystalline metallic surfaces was characterized by atomic stick-slip [5].…”

Thermally Activated Contact Strengthening Explains Nonmonotonic Temperature and Velocity Dependence of Atomic Friction

“…[14,15], unraveling the underlying specific molecular processes in quantitative detail. Further possible aging mechanisms are the formation of capillary bridges in a humid environment [16] and the formation of a neck due to material transfer from the substrate into the contact region with the tip [17]. Finally, recent molecular-dynamics simulations revealed that the AFM tip may, in the course of time, evolve into a different geometrical contact configuration characterized by a different energy of binding to the surface [18].…”

“…The basic idea of our model is that, in any given stick phase, the tip-sample contact may either break, resulting in a slip event, or strengthen itself by one of the molecular aging mechanisms described above [13][14][15][16][17][18]. Within our minimal model, we assume just two possible stick states of the AFM tip: a weakly bound state A and a strongly bound state B (see Fig.…”