AFM dissipation topography of soliton superstructures in adsorbed overlayers

Abstract

In the atomic force microscope, the nanoscale force topography of even complex surface superstructures is extracted by the changing vibration frequency of a scanning tip. An alternative dissipation topography with similar or even better contrast has been demonstrated recently by mapping the ͑x , y͒-dependent tip damping but the detailed damping mechanism is still unknown. Here we identify two different tip dissipation mechanisms: local mechanical softness and hysteresis. Motivated by recent data, we describe both of them in a onedimensional model of Moiré superstructures of incommensurate overlayers. Local softness at "soliton" defects yields a dissipation contrast that can be much larger than the corresponding density or corrugation contrast. At realistically low vibration frequencies, however, a much stronger and more effective dissipation is caused by the tip-induced nonlinear jumping of the soliton, naturally developing bistability and hysteresis. Signatures of this mechanism are proposed for experimental identification.

Recent highlights in nanoscale and mesoscale friction

“…Particularly when the FFM tip is subject to stick–slip advancement, this mode becomes especially efficient for resolving structural features. By mapping the power dissipated by these lateral forces, FFM can even detect such elusive structures as moiré patterns on a lattice-mismatched crystal overlayer [ 10 – 12 ]. One of the most frequent motivations to utilize FFM as a tool in nanotribology is its ability to mimic a single-asperity contact by the junction between a sharp AFM tip and the substrate.…”

Atomic Friction Modulation on the Reconstructed Au(111) Surface

“…1a). As an example, using a one-dimensional model consisting of an elastic chain being dragged over a rigid substrate, Negri et al recently showed that friction amplitude modulation could be caused by local mechanical softness and hysteresis at surface defects [27]. This also described friction force variations seen on ultrathin KBr films that had superstructures being deposited on the lattice-mismatched substrates [20].…”

Modeling friction: From nanoscale to mesoscale

“…Noncontact AFM tips oscillating on top of kink-like adsorbate regions (Maier et al, 2008) dissipate significantly more than near in-registry regions. This mechanism is explained by the higher softness and mobility of solitonic regions (Bennewitz et al, 2000;Gauthier and Tsukada, 2000;Hoffmann et al, 2001;Loppacher et al, 2000), and it has been demonstrated by the dynamics of an incommensurate FK chain, forced and probed by a locallyacting oscillation (Negri et al, 2010).…”