Nanotribological Properties of Hexadecanethiol Self-Assembled Monolayers on Au(111): Structure, Temperature, and Velocity

Abstract

Self-assembled monolayers (SAM) are promising building blocks for the optimization of a large variety of systems both on the nano- and on the microscale. Among other applications, SAM are often used as protective coating or friction modifiers. In this work, we have used hexadecanethiol SAM on Au(111) as a model system and studied the different mechanisms of energy dissipation during temperature and velocity dependent friction force microscopy (FFM). In a number of cases, the SAM remained stable during atomic force microscopy experiments and friction-velocity isotherms related dissipation to an activation energy. In other cases, friction experiments lead to an irreversible deterioration of the SAM. This can rather be associated with the general SAM structure that was analyzed by scanning tunneling microscopy and showed a large variety of potential breakdown points like, for example, grain boundaries, step edges, or substrate-related holes in the SAM.

Atomistic modeling of tribological properties of Pd and Al nanoparticles on a graphene surface

“…This results from the different lattice constant and atomic arrangements in Al and Pd particles. A similar non-monotonous behavior of friction is observed for hexadecanethiol self-assembled monolayers on Au substrates [ 4 ] and NaCl(001) crystal surfaces in ultrahigh vacuum [ 5 ].…”

“…It was noted that the substrate force that acts on the nanoparticle has a sawtooth form as a function of coordinate (and time) as is also observed in nanotribological experiments [ 6 , 13 – 14 ]. We have studied the temperature dependence of friction, which is similar to that of hexadecanethiol self-assembled monolayers on Au substrates [ 4 ] and NaCl crystal surfaces in ultrahigh vacuum [ 5 ].…”

“…There are many studies concerning the tribological properties of nanoobjects. For example, alumina nanoparticles were studied in [ 9 ] and self-organized monolayers in [ 4 ]. In [ 5 ] the authors studied the interaction in ultrahigh vacuum between a nanoasperity and an alkali-metal halide surface at different temperatures, and showed how the static friction and contact stiffness depend on the contact area.…”

Friction of Methyl-Branched Fatty Acid Layers at Low and High Sliding Speeds

“…If the contact stays at a film thickness where boundary lubrication occurs, which is the situation in the experiments presented here, then the friction force is often found to increase with increasing sliding speed. Studies of self-assembled structures over large ranges of speed have thus far mostly been done with AFM. − Several different phenomena may contribute to the increase in friction force. If the boundary layer can be viewed as a viscous film, an increase in speed may produce a shift in the friction response from fluid-like to more rubber-like.…”

Fabrication of a Polymer Nano Nozzle for Electrohydrodynamic Small-Molecule Solvent Inkjet Printing

“…When increasing the voltage so that the normal electrical stress is greater than the surface tension, the meniscus deforms to a stable conical shape, and a charged fine jet less than the diameter of the nozzle is ejected from the nozzle (Figure a inset). Once ejected, the droplets of 1-hexadecanethiol deposited on the substrate will form a dense self-assembled layer with Au. , When the substrate was etched in the Au etchant (I 2 /KI/H 2 O = 4 g:20 g:200 g) for 10 s, only Au with 1-hexadecanethiol droplets deposited on the surface was left. Thus, high-resolution Au patterns and some structures fabricated based on this are also available.…”