Subcategory: Materials Science
Jasmine Daniels - Texas Southern University
Co-Author(s): Sean P. Dillon, Erika Fuentes, Sara M. Rupich, and Yves J. Chabal, University of Texas at Dallas
Self-assembled monolayers (SAMs) are highly-ordered, densely-packed, organic molecules covalently bound to a substrate such as Silicon. Organic based SAMs allow for fabrication of low cost devices of ever decreasing dimensions, useful in areas such as photovoltaics, sensors, and logic devices. The densely packed SAM ensures passivation of the underlying silicon interface and prevents oxidation. On Silicon, SAMs are formed via a hydrosilylation reaction in which an alkene reacts with a H-terminated Si surface through thermal or Ultraviolet (UV) activation. The use of bifunctional alkenes allows preparation of surfaces that can be used for subsequent modifications such as Atomic Layer Deposition (ALD) or layer-by-layer assembly. The choice of bifunctional molecule is critical as the alkene must be more reactive than the other end group. In previous studies, an ester was used which could later be transformed into a reactive carboxylic acid moiety. However, these additional steps introduce the possibility of etching or oxidation. It was proposed to graft 1,2-epoxy-9-decene to the silicon surface to eliminate the multiple step process while maintaining high packing density and reactivity of the surface moiety. Here, we study the reaction between H-termianted Si(111) and 1,2-epoxy-9-decene. A hydrosilylation reaction is used to covalently bond SAMs of 1,2-epoxy-9-decene to oxide-free H-terminated Si surfaces through thermal applications or Ultraviolet (UV) radiation. Additionally, we prepared model surfaces using 1,7-Octadiene and Butyl Vinyl Ether to investigate molecules with a lone binding mechanism yet still possess similarities with the epoxide. The prepared SAMs were studied via Fourier Transform Infrared Spectroscopy (FTIR), Attenuated Total Reflectance FTIR spectroscopy (ATR-FTIR), ellipsometry, and X-ray photoelectron spectroscopy (XPS) to characterize the surface. From these studies, we found that the epoxide binds to the silicon surface bonds in complex and unexpected ways.
Funder Acknowledgement(s): National Science Foundation Grant (NSF) No. DMR1156423 and DMR1460654 for their financial support.
Faculty Advisor: Yves Chabal, Wilson_BL@tsu.edu
Role: I participated all operations of the project, excluding developing the project itself.