Micro/nano-tribological characteristics of self-assembled monolayer and its application in nano-structure fabrication

The fundamental tribological characteristics of 1H,1H,2H,2H-perfluorodecyltrichlorosilane (FDTS), octadecyltrichlorosilane (OTS), and single chain alkanethiol self-assembled monolayers (SAMs) with various chain lengths were investigated in order to identify the mechanical scribing condition for micro-machining applications. The concept of the novel surface micro-machining explored in this work is to mechanical scribe away the SAM resist coated on the workpiece surface where, pattern formation by subsequent chemical etching is desired. From the experimental results, it was found that the FDTS surface was damaged about 20% more rapidly than the OTS surface due to higher friction, even though the surface energy of FDTS was lower than that of OTS. Also, it was found that thiol on a copper surface could be removed even under a few nN normal load. The nano-tribological characteristics of alkanethiol SAM on various metals were largely dependent on the native oxide layer of metals. Based on these findings, FDTS and 1-hexadecanethiol (HDT) were chosen as the resists for silicon and metal surfaces, respectively. By using the mechano-chemical process with a diamond-coated tip, nano-patterns with sub-micrometer width and depth on surfaces of Au, Ag, Cu and Si could be fabricated.