Amplitude Nanofriction Spectroscopy

Friction at the macroscopic scale originates from the mechanical and tribological response of single micro- to nano-scale single contacts. Consequently atomic scale friction rises as an indispensable component for large scale friction understanding as well as for the ever-growing nanotechnology fields. The interfacial sliding dynamics bears several successive live phases: from static pinning, to depinning and transient evolution, eventually ushering in steady state kinetic friction. While standard tip-based atomic force microscopy generally addresses the steady state, the prior intermediate steps are much less explored. We present here an experimental and simulation approach, taking advantage of a high frequency oscillatory imposed strain to obtain a one-shot investigation of all these successive interfacial responses. Few atoms gold contacts sliding on graphite are used to uncover the phenomena that bridge the gap between initial depinning and large speed sliding. Our findings unveil dynamical response reminiscent of thermolubric behavior at very small contact size and superlubric response for contacts larger than the graphic unit cell. The results pave the way to important insights in the understanding of atomic scale time and magnitude dependent rheology.