Observation of self‐assembled monolayers on diamond‐like carbon films: agglomeration of self‐assembled FDTS molecules

Abstract

AbstractSelf‐assembled monolayers (SAMs) of 1H,1H,2H,2H‐perfluorodecyltrichlorosilane (FDTS) were prepared on hydrogen‐free diamond‐like carbon (DLC) films by immersing the DLC substrates into dilute solutions of FDTS in hydrofluoroether. The FDTS‐adsorbed DLC surfaces were observed using a tapping mode atomic force microscopy (AFM) with respect to the immersion time to investigate the monolayer formation process. The measurements of the water contact angles, X‐ray photoelectron spectroscopy (XPS) and the surface roughness were also conducted. The DLC films were deposited on silicon plates with an electron cyclotron resonance(ECR)‐type ion beam sputter using graphite as a sputter target. Initially, FDTS molecules form a liquid‐like disordered mass of molecules on the DLC surface, and then begin to form densely packed FDTS islands with the height of a monolayer. The FDTS monolayer islands grow laterally with the immersion time. After immersion for several hours, the agglomeration of FDTS molecules to a height of 3–5 nm is observed on the DLC surfaces. This is due to the presence of a large number of active sites on the hydrogen‐free DLC surface, preventing the surface diffusion of FDTS molecules. Also, the inhomogeneity of the DLC surface due to the adsorption of a large number of oxygen atoms from the air after DLC deposition is one of the reasons for the FDTS agglomeration. Copyright © 2010 John Wiley & Sons, Ltd.