Covalently bound fluorine-containing monolayers on silicon and oxides : formation, stability and tribology

The formation of fluorinated monolayers with a minimized surface energy and an improved chemical stability on specific substrates will enable outstanding tribological properties and is the main goal of the research described in this thesis. Inorganic substrates, such as Si(111), silicon carbide (SiC), chromium nitride (CrN), and organic nano-micro-textured substrates such as PMMA, PDMS, PS and PEEK have been studied. Both fluorinated and non-fluorinated monolayers with a high packing density were obtained using functionally different surface attaching groups like alkenes, alkynes, enynes, silanes, and phosphonates. Most of these attaching moieties have been used before, but the deepening understanding of the factors that determine monolayer qualities allowed the development of even better attaching groups, like the ynenes.

Newly synthesized fluorinated alkyne-derived monolayers will be described exhibiting a minimized surface energy and an exceptionally low critical surface tension. The chemical stability in various aqueous media at different temperatures was also studied. Nano-tribology measurements were performed using atomic force microscopy (AFM) to verify a minimum in adhesion, friction and wear. The organic monolayers obtained on various surfaces in this study will be useful in MEMS/NEMS high performance industrial applications.