Nanoscale Friction Varied by Isotopic Shifting of Surface Vibrational Frequencies

Abstract

Friction converts kinetic energy at sliding interfaces into lattice vibrations, but the detailed mechanisms of this process remain unresolved. Atomic force microscopy measurements reveal that changing the mass of the terminating atoms on a surface, and thus their vibrational frequencies, affects nanoscale friction substantially. We compared hydrogen- and deuterium-terminated single-crystal diamond and silicon surfaces, and in all cases the hydrogenated surface exhibited higher friction. This result implies that the lower natural frequency of chemisorbed deuterium reduces the rate at which the tip's kinetic energy is dissipated. This discovery is consistent with a model describing energy transfer to adsorbates from a moving surface.

Mechanical stiffness and dissipation in ultrananocrystalline diamond microresonators

“…3 Most of this sp 2 -bonded carbon is present at the grain boundaries; some fraction may be due to adsorbates and surface reconstruction. Hydrogen termination 29 of the surface using a hot filament process resulted in the reduction in sp 2 content in the near-surface region to 4.3%. Thus, this percentage represents a likely lower bound for the sp 2 content of the bulk of the film assuming a uniform film structure with thickness.…”

From ice superlubricity to quantum friction: Electronic repulsivity and phononic elasticity

“…16. The additional neutron in the 2 H + plays a certain yet unclear role of significance because of the possible mass difference between the H and 2 H adsorbates [88]. In fact, adsorption of the isotope lowers the vibration frequency by 2 −1/2 of the adsorbate on substrate by folding the reduced mass of the oscillator, which reduces the friction coefficient [36].…”

“…The occurrence of quantum friction is a kinetic process of energy dissipation (E = f r s with f r being the friction force and s the sliding distance) due to the phonon (heat) and electron excitation (electron−hole pair production) during sliding [88]. A state of ultralow friction is reached when a sharp tip slides over a flat surface and the applied pressure is below a certain threshold, whose value is dependent on the surface potential sensed by the tip and the stiffness of the contacting materials [89−91].…”

Influence of the chemical surface structure on the nanoscale friction in plasma nitrided and post-oxidized ferrous alloy

“…In fact, incorporation of fundamental physical concepts at the nanoscale friction studies started two decades ago. [4][5][6][7] Recently, by applying a chemical approach, a qualitative correlation between the friction coefficient of several oxides with the ionic surface potential relationship was established. 8,9 Also, the influence of phonons has been incorporated in the effort to understand the friction phenomenon at the nanoscale level, i.e., by considering the excitation of vibrational modes of the atoms bonded at the studied surfaces.…”

“…1 From a physicochemical point of view, the macroscopic properties cited above can be understood in terms of elementary interactions such as attractive forces (Van der Waals), strength and stiffness of chemical bonds, thermal (electrical) conductivities involving phonons coupling, and electronic band structures. 7 According to recent models considering elementary vibrational frequencies modes of bonded atoms forming the outermost layer of the material, the friction force due to vibrational damping is giving by F ¼ mgv, where g ¼ mx 4 /2pq C T 3 is the damping constant in the case of a single adsorbate 5 and g ? ¼ mx 2 n a /q C L in the case of ordered commensurate adsorbate layers with longitudinal elastic waves.…”