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Electron Transfer Initiated Formation of Covalently Bound Organic Layers on Silicon Surfaces
journal contribution
posted on 2014-09-11, 00:00 authored by Kallum
M. Koczkur, Emad M. Hamed, M’hamed Chahma, Daniel
F. Thomas, Abdelaziz HoumamAn
electron transfer initiated organic modification of silicon
surfaces, using a donor/acceptor pair of ferrocene (Fc) and N-bromosuccinimide (NBS) (or N-bromophthalimide
(NBP)), is reported for the first time. This modification method is
efficient and does not require the use of heat or irradiation. Multilayer
structures are formed on the surfaces through radical reactions, similar
to the reduction of aryl diazonium salts. The modified surfaces were
characterized by infrared reflection–absorption spectroscopy
(IRRAS), X-ray photoelectron spectroscopy (XPS), and atomic force
microscopy (AFM). IRRAS spectra clearly indicate a strong carbonyl
stretch and the presence of a ferrocene moiety for each of the modified
surfaces. XPS data show the presence of all elements from the donor/acceptor
pair and provide strong evidence that the samples can be further modified
by nucleophilic substitution. AFM imaging indicates the formation
of dense layers that can be scratched away to reveal depth information
on approximately 2 nm and the underlying terraces of the silicon substrate.
A mechanism is proposed where radical abstraction of a surface hydrogen
takes place leading to the formation of a covalently bound imidyl
group, which is followed by the formation of polymeric structures
through radical chain reactions.
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Keywords
chain reactionselectron Transfer Initiated Formationcarbonyl stretchnucleophilic substitutionMultilayer structuresIRRAS spectramodification methodNBSsurface hydrogenpresenceAFM imagingaryl diazonium saltsSilicon SurfacesAn electron transferNBPCovalently Bound Organic Layersimidyl groupdepth informationspectroscopy2 nmsilicon surfacesdonorforce microscopyXPS data showsilicon substrateferrocene moiety
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