Web Release Date: April 20,
Phase Separation of a Mixed Self-Assembled Monolayer Prepared via a Stepwise Method
and
School of Chemical and Biological Engineering, Institute of Chemical Processes, Seoul National University, San 56-1, Shillim, Kwanak, Seoul 151-742, Korea, and Department of Chemical Engineering, Kwangwoon University, Seoul 139-701, Korea
Received July 19, 2005
In Final Form: March 26, 2006
Abstract:
Self-assembled monolayers (SAMs), a molecular-level assembly that forms spontaneously, provide a vehicle for investigating specific interactions at interfaces. This is particularly true for mixed SAMs that are composed of organosilanes with different chain lengths and/or chemical functionalities because they offer an adjustable surface for constructing 3D structures containing a variety of moieties. We recently observed that coadsorbed monolayers with different organosilanes on a Si wafer were separated into several tens or hundreds of nanometer domains that were rich in individual components. Several organosilanes, such as octadecyltrichlorosilane (OTS), octadecyltrimethoxysilane (OTMS), (3-mercaptopropyl)trimethoxysilane (MPTMS), and (3-aminopropryl)trimethoxysilane (APTMS), were used for regional separation. In this study, we propose a stepwise deposition method, namely, the deposition of a second siliane on a SAM substrate that creates intentional defects in the first silane. The surface morphologies were adjusted by the deposition sequence and immersion time of the silanes. As a result, a mixed SAM prepared by the proposed method showed effectively functionalized films compared to that prepared by the one-step method.
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