Microscopic Friction Studies on Metal Surfaces

Abstract

Atomically flat and clean metal surfaces exhibit a regime of ultra-low friction at low normal loads. Atomic force microscopy, performed in ultra-high vacuum on Cu(100) and Au(111) surfaces, reveals a clear stick-slip modulation in the lateral force but almost zero dissipation. Significant friction is observed only for higher loads (*4-6 nN above the pull-off force) together with the onset of wear. We discuss the minor role of thermal activation in the low friction regime and suggest that a compliant metallic neck between tip and surface is formed which brings upon the low, load-independent shear stress.

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

“…In Ref. [5], the authors investigated the sliding friction behavior of single crystalline metallic surfaces by AFM under UHVconditions and by using a SiO x tip as a single-asperity counter-body. There, the friction force was observed to vanish in the adhesive regime.…”

“…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].…”

“…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]. Further the effect of surface modifications on the nanotribology of Au(111) has been investigated and compared to the nanotribological response of a clean Au(111) surface [7].…”

“…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.…”

Nanoscale Friction Behavior of the Ni-Film/Substrate System Under Scratching Using MD Simulation

“…In the experiment by Gosvami et al [28], the atomically flat metal surface was found to exhibit very low frictional dissipation over a range of several nanonewtons, and there was almost no surface damage observed during low-load scratch measurements. Our results suggest that the highsurface mobility of atoms can be taken as one of the reasons why the flat metal surface exhibits very low frictional dissipation-namely, it can restore the metal surfaces during the shallow scratch process.…”