AVS 58th Annual International Symposium and Exhibition
    Electronic Materials and Processing Division Thursday Sessions
       Session EM-ThP

Paper EM-ThP21
Small-Molecule Scaffolds for Directed Self-Assembly

Thursday, November 3, 2011, 6:00 pm, Room East Exhibit Hall

Session: Electronic Materials and Processing Poster Session
Presenter: Pablo Mancheno-Posso, University of Arizona
Authors: P. Mancheno-Posso, University of Arizona
A.J. Muscat, University of Arizona
Correspondent: Click to Email
Self-assembled monolayers (SAMs) are often used as scaffolds for the deposition of a subsequent layer. This process allows the surface properties to be tailored to a specific application and facilitates the construction of functional nanostructures. For instance, copper electrodes and graphene have been deposited on carboxyl-terminated and on 3-aminopropyltriethoxysilane (APTES) monolayers, to create metallic electrodes for electronic devices and a lubricating layer for nanoelectromechanical systems, respectively. Small silane molecules in particular could be used to direct the self-assembly of another layer and keep it in close proximity to a silicon surface. Vinyltrichlorosilane (VTCS, CH2=CH-SiCl3) is a candidate and contains a carbon-carbon double bond. A vinyl C=C bond is a versatile functional group because it can be reacted in situ to generate a variety of terminations, including –COOH, –SH, and –NH2, and could also direct the assembly of new molecules on the surface. While VTCS SAMs have been studied previously, a reproducible and self-limiting process to form a single monolayer from solution has not yet been achieved. In this work we adsorbed VTCS from solution on a Si(100) substrate and characterized the layer with ellipsometry, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). Silicon wafers were cleaned and hydroxylated in a piranha solution. After drying, the samples were dipped for different times into a 1:1000 solution of VTCS in toluene, hexane, chloroform and acetone. The thickness of the monolayer was monitored ex situ using ellipsometry. Toluene and hexane yielded multilayers with a thickness greater than 10 Å, whereas chloroform and acetone produced more consistent monolayers with a thickness of about 6 Å. A bromination was performed to demonstrate the presence of the unsaturated bond. We are in the process of making XPS and AFM measurements to determine whether VTCS is covalently attached to the Si substrate and to assess whether the vinyl group is suitable to graft molecules to the substrate.