Physical and chemical properties of organic monolayers on silicon oxide and gold surfaces

The formation of organic monolayers on the silicon and silicon oxide surface is important in several technological areas such as microelectromechanical systems (MEMS), microfluidics, and biochip arrays. Organic monolayers allow one to tailor the surface chemical and physical properties at the molecular level. In this thesis work, a new strategy to modify silicon and silicon oxide surfaces with organic monolayers has been developed. This two-step surface functionalization method involves the chlorination of the silicon oxide surface to give Si-Cl bonds which then react with the hydroxyl groups of alcohol molecules resulting in monolayer formation via Si-O linkages.; Interfacial force microscopy (IFM) was used to investigate the tribological properties of films that were capped with a methyl group. These films resulted in surfaces with an exceptionally low friction coefficient. Friction was shown to increase as the alkyl chain length of the monolayer precursors decreased. The interfacial mechanical properties were correlated to molecular structures at the interface between film and tip. Wear studies also showed these films to be quite durable.; Organic monolayers were also used as models for thermodynamic studies in 2D. When a metal ion is adsorbed onto a functionalized surface, the metal ion may interact with more than one surface group, resulting in a “surface chelating effect”. X-ray photoelectron spectroscopy (XPS) was used to monitor the adsorption of metal ions to carboxylic acid functionalized surfaces in the presence of a solution phase metal ion scavenger. A chelating effect was observed at the surface and was attributed to the presence of a two-dimensional array of ligands on the surface.