AVS 46th International Symposium
    Surface Science Division Friday Sessions
       Session SS1+AS+BI-FrM

Paper SS1+AS+BI-FrM8
Self-assembled Monolayers on Silicon Surfaces: The Opposite to Siloxane Chemistry

Friday, October 29, 1999, 10:40 am, Room 606

Session: Organic Films/Self-Assembled Monolayers
Presenter: J.A. Mulder, University of Minnesota
Authors: J.A. Mulder, University of Minnesota
R.P. Hsung, University of Minnesota
X.-Y. Zhu, University of Minnesota
Correspondent: Click to Email
Self-assembled monolayers (SAMs) on silicon surfaces are of interest for a number of reasons: they may be used as monolayer resists in high resolution lithography, as dielectric layers, as active components in hybrid sensor devices, as passivation and lubrication layers in MEMS, and as a new platform for biochips. SAMs on silicon are traditionally formed via siloxane chemistry on oxidized surfaces from organosilicon derivatives, such as alkyltrichlorosilane. The problems with siloxane SAMs are well known: they are difficult to prepare and suffer from poor reproducibility; the contradiction between cross-linking and close-packing is inherent; the presence of the amorphous and insulating oxide layer is not desirable in some applications. There is much incen tive to develop simple processes for the formation of stable molecular layers directly on the silicon surface. We present a novel approach which, in essence, is the opposite to the siloxane SAM process. The assembly processes are based on the reaction bet ween R-OH or R-NH2 with chlorinated silicon surfaces, leading to molecular assembly via Si-O or Si-N linkages. These reactions are not only efficient but also sufficiently versatile for the assembly of a wide variety of functional organic molecules. A par ticular advantage of this new assembly chemistry is that it is compatible with both vacuum and solution phases and can be carried out under very benign experimental conditions. We characterize these SAMs using a variety of techniques, such as multiple-int ernal reflection FTIR, X-ray photoelectron spectroscopy, contact angle measurements, and scanning probe microscopy. We address structural and stability of these SAMs and their dependence on molecular structure, such as alkyls and aromatics. We also discuss immediate and future applications.