Influence of Alkali Ions on Tribological Properties of Silicon Surface

Abstract

Tribological properties of surfaces (friction, adhesion and wear) provide challenging limitations to the design of reliable machines on the micro-and nanometer scale as the surface to volume area increases and volume, mass and inertia of the mobile parts decrease. This study reports on the reduction in the friction force of silicon surfaces after the alkali metal ion exposure in the form of aqueous solutions. A scanning force microscope equipped with a liquid cell was used to investigate the friction force and the pull-off force of a flat silicon surface immersed in water and in different alkali metal chlorides solutions: LiCl, NaCl and CsCl. The concentration ranged from 0.1 up to 1000 lmol/l. The changes in the free surface energy of the initial surface and of the modified surfaces after drying were determined from contact angle measurements and from the acid-base adhesion theory. In both cases, in the liquid environment and after drying of the exposed silicon substrates in air, the friction force is reduced by approximately 50 %. Our results provide new, fundamental insight into the exchange of surface termination layers in particular for tribology. Also it is suggested to use the procedure as a low-cost alternative to improve the tribological properties of the silicon surface in particular in applications where lubricating fluids are not appropriate, e.g., in nanomachines and devices.

Removal of As(V) Based on Amino-Group Surface-Functionalized Porous Silicon Derived from Photovoltaic Silicon Cutting Powder

“…Porous silicon can be used for modification of organic functional molecules due to its large specific surface area and more active groups (Si-OH) on the surface [20][21][22], which can also be used as a potential adsorbent substrate material. According to a research report by Dariusz M. Jarzabek, et al, the friction performance of the silicon surface was greatly improved when the porous silicon was exposed to an aqueous solution of alkali metal ions [23]. On the other hand, the organic modification of the hydrogen-terminated silicon surface summarized by Danial D. M. Wayner et al also provides more possibilities for the application of modified porous silicon [24].…”