Atomic-Scale Wear in UHV: Connection Between AFM Induced-Abrasion and Debris Recrystallization

Abstract

Recent Ultrahigh Vacuum (UHV) scratching Atomic Force Microscopy (AFM) experiments showed the formation of regular patterns composed by small atomic clusters or mounds located around the surfaces being scanned. The formation of such structures has been theoretically reproduced and explained as, mainly produced by the flux of adatoms generated by the AFM tip stripping off adatoms during the continuous passage of the probe tip on the analysed surface. The homoepitaxy growth process on Aluminium was used for the identification of the direct connection between the adatoms flux due to wear mechanisms and the self-assembled growth processes. Such theoretical results were based on the general assumption that surface diffusion is the dominant transport mechanism of mass, and a nonequilibrium thermodynamics framework for the self-organized growth process has been developed showing evidence of the direct connection between the growth structures due to atomic debris formation and the flux of the atomic debris due to the activated wear mechanisms. In this article, we revisit the preview model giving new contributions to it and, in turn, we suggest that the improved model as proposed in this article can be supported with a new class of experiments for the quantification of the wear rates occurring for AFM probe tips in UHV conditions. In turn, a general review on activated wear mechanisms is briefly discussed.

Nanoscale rippling on polymer surfaces induced by AFM manipulation

“…Nanoscale ripples have been then observed after performing one or many scans over the same area on a wide range of materials, namely ionic salts, metals, and semiconductors [ 6 – 9 ]. Regarding some crystalline materials, D’Acunto [ 10 – 11 ] and Filippov et al [ 12 ] have successfully reproduced the experimental data via computational methods. Nevertheless, it is for polymeric films that the ripple formation has been studied most extensively [ 13 – 19 ].…”

Near-field surface plasmon field enhancement induced by rippled surfaces

“…The physics of the growth and of the subsequent patterning process can be described by a damped Kuramoto–Sivashinsky (DKS) equation [45–47]. We propose a finite-difference semi-implicit splitting scheme of second order in time and space to numerically solve the DKS equations, with phenomenological parameters.…”

“…Rippled surfaces describing growth processes subsequent to deposition rates as, for example, with the IBS technique or other equivalent patterning methods is a nonequilibrium process where a two-dimensional surface is defined by the height function h ( x , y , t ), whose evolution in time is monitored. The physics of the growth and of the subsequent patterning process can be described by a damped Kuramoto–Sivashinsky (DKS) equation [ 45 – 47 ]. We propose a finite-difference semi-implicit splitting scheme of second order in time and space to numerically solve the DKS equations, with phenomenological parameters.…”

“…In the last decades several models have been proposed for describing the dynamic behavior of growing surfaces and corresponding patterns. In all such methods, the common approach is to asymptotically reduce the partial differential equations governing the complex growing dynamics to a sample equation for the interface [ 44 – 45 ]. One critical point in all such methods is represented by the choice of parameters to be included in the partial differential equations, and in many cases, such parameters must be chosen empirically.…”