Delivering octadecylphosphonic acid self-assembled monolayers on a Si wafer and other oxide surfaces.
We describe a simple experimental approach for delivering self-assembled monolayers (SAMs) of octadecylphosphonic acid (OPA) on many oxide surfaces using a nonpolar medium with a dielectric constant around 4 (e.g., trichloroethylene). This approach readily results in the formation of full-coverage OPA SAMs on a wide variety of oxide surfaces including cleaved mica, Si wafer, quartz, and aluminum. Especially, the availability of delivering full-coverage OPA SAM on a Si wafer is unique, as no OPA SAMs at all could be formed on a Si wafer when using a polar OPA solution. The reason a nonpolar solvent is superior lies in the very fact that the hydrophilic OPA headgroup tends to escape from the nonpolar solution and is thus enriched at the medium-air interface. It is these OPA headgroups seeking a hydrophilic surface that make possible the well-controlled OPA monolayer on an oxide surface.
Nie
Heng-Yong
HY
Surface Science Western, Room G-1, WSC, The University of Western Ontario, London, Ontario N6A 5B7, Canada. hnie@uwo.ca
Walzak
Mary J
MJ
McIntyre
N Stewart
NS