X-Ray Specular Reflection Studies of Silicon Coated by Organic Monolayers (Alkylsiloxanes)
Abstract
X-ray specular reflectivity is used to characterize the structure of silicon/silicon-oxide surfaces coated with chemisorbed hydrocarbon monolayer films (alkylsiloxanes). Using synchrotron radiation the reflectivity could be followed over 9 orders of magnitude, from grazing incidence to an incident angle allowing a spatial resolution of features along the surface normal. Analysis was performed by fitting the data to reflectivities calculated from models of the surface electron density and by calculation of Patterson functions directly from the data. These procedures allow identification of an approx 17 Angstrom thick SiO2 layer, a layer of head group region where the alkyl siloxane adsorbs to the SiO2, and the hydrocarbon layer. The data also requires that the various interface have different widths. the fact that the same local hydrocarbon density is observed for both fully formed and partially formed monolayers with alkane chains of varying length excludes a model in which the partially formed monolayer is made up of separated islands of well formed monolayers. Measurements before and after chemical reaction of a monolayer in which the alkyl chain is terminated by an olefinic group demonstrates the ability to use x-ray reflectivity to characterize chemical changes. Effects of radiation damage on these types of measurements are described.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 01, 1989
- Accession Number
- ADA217418
Entities
People
- B. M. Ocko
- G. M. Whitesides
- I. M. Tidswell
- J. D. Axe
- P. S. Pershan
- S. R. Wasserman
Organizations
- Harvard University