Multi-asperity Nanotribology of Self-Assembled Monolayers Grafted on Silicon Wafers Displaying Various Crystallographic Orientations and Nanostructures

Abstract

International audienceMicro/nanotribological study of self-assembled monolayers (SAMs) derived from n-alkyltrichlorosilanes deposited on silicon wafers displaying various crystallographic orientations-Si (100), Si (111) and Si (110)-has been conducted using a ball-on-disc nanotribometer. The parameters that have been varied are (i) the alkyl chain length, (ii) the tribological parameters (i.e. the normal load, the sliding velocity, the sliding distance and the relative humidity level) and (iii) some surface characteristics of the silicon substrates (i.e. crystallographic orientation, roughness, and thickness of the amorphous native oxide). Experimental results show that the key parameter controlling the tribological behaviour is not the alkyl chain length as generally reported for adsorbed and grafted monolayers, but rather the film's homogeneity-i.e. the degree of packing and the surface coverage of the monolayer-in connection with the crystallographic orientation of the substrate

Comparative study of nitrogen implantation effect on mechanical and tribological properties of Ti-6Al-4V and Ti-10Zr-10Nb-5Ta alloys

“…Hardness and Young's modulus values were obtained using a CSM Instruments Nanoindention Tester. Friction tests have been conducted using an experimental device constituted by a ball-on-disc nano-tribometer that has been presented in previous papers [28,29]. Tests were carried out at ambient air and room temperature under an applied load of 100 mN .The riders were spheres of polycrystalline alumina (hardness: 1650 HV) or 100Cr6 steel (hardness: 720 HV) with a diameter of 1.5 mm.…”

Thermal-Controlled Frictional Behaviour of Nanopatterned Self-assembled Monolayers as Triboactive Surfaces

“…For instance, photo-and thermo-activated self-assembled monolayers (SAM) seem to be a promising way for this purpose [9,10,11,12,13] assuming that suitable functional groups can be found or synthesized for each given application. Indeed, selfassembled monolayers have been used for long to both reduce wear [18,19,20,21,22] and friction [20,21,23,24,25,26,27] in MEMS but, as far as we know, always as a passive way -ie, without any dynamic external control. The principle of this control mainly consists in influencing the dissipation mechanisms within the contact by acting on the reversible order-disorder changes at the molecular scale.…”

“…In this work, octadecyltrichlorosilane self-assembled monolayer -so-called OTS SAM -will be used as a model of triboactive surfaces. This SAM reveals an interesting peculiar thermal-controlled frictional behaviour [9] and a good frictional behaviour in MEMS tribological conditions [18,19,21,22,23,24,25,26,27]. Unfortunately, it is well known that OTS SAM displays a limited lifespan especially as a continuous monolayer [27] mainly because its entangled molecules [30,31] involve high stresses within the sub-surfaces which, in turn quickly induce substrate seizure [32], especially in case of silicon wafers [27].…”

“…This SAM reveals an interesting peculiar thermal-controlled frictional behaviour [9] and a good frictional behaviour in MEMS tribological conditions [18,19,21,22,23,24,25,26,27]. Unfortunately, it is well known that OTS SAM displays a limited lifespan especially as a continuous monolayer [27] mainly because its entangled molecules [30,31] involve high stresses within the sub-surfaces which, in turn quickly induce substrate seizure [32], especially in case of silicon wafers [27]. To avoid this issue, periodic nano-patterned triboactive surfaces have been designed by grafting OTS SAM using micro-contact printing (µCP) [33,34,35,36,37,38,39,40,41].…”

Multi-axis MEMS force sensor for measuring friction components involved in dexterous micromanipulation: design and optimisation

“…This approach was well suitable for studying the sliding component but is clearly inadequate for assessing several frictional components simultaneously. Among the other existing tribometers [14,15,16,17], the Tribolever proposed by Zijlstra [18] is well designed to characterize sliding components. It is composed of a central detection pyramid surrounded by four high aspect ratio legs.…”