AFM Dissipation Topography of Soliton Superstructures in Adsorbed Overlayers

TL;DR

This paper investigates the dissipation mechanisms in atomic force microscopy of soliton superstructures, identifying local softness and hysteresis as key factors, and models their effects to improve contrast in surface topography imaging.

Contribution

It introduces a one-dimensional model explaining two dissipation mechanisms—local softness and hysteresis—in AFM of incommensurate overlayers, enhancing understanding of dissipation contrast.

Findings

Local softness at soliton defects increases dissipation contrast.

Hysteresis from tip-induced nonlinear soliton jumping causes strong dissipation.

Signatures for experimental identification of these mechanisms are proposed.

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,y)-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 Moire' 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.