X-Ray Damage to CF3CO2-Terminated Organic Monolayers on Si/Au Supports is due Primarily to X-Ray Induced Electrons
HARVARD UNIV CAMBRIDGE MA
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X rays damage organic materials. The relative importance of X rays themselves, and of both X ray generated and secondary electrons, in this damage was explored using self-assembled monolayers SAMs on multilayer thin film supports. The substrates were prepared by depositing thin films of Si 0, 50, 100 and 200 on thick layers of Au 2000 Angstroms these systems were supported on chromium-primed silicon wafers. Trifluoroacetyl-terminated SAMs were assembled on these substrates and the samples irradiated with monochromatic A1 Kalpha X-rays. The fluxes of X rays to which the different samples were exposed were the same, but the fluxes and energy distributions of the electrons generated by interactions of the X rays with the substrates differed. The loss of fluorine from the SAMs was followed by XPS and was slower on substrates emitting a lower flux of electrons. This observation indicated that the electrons, and not the X rays themselves, were largely responsible for the damage to the organic monolayer films that resulted in loss of fluorine from them.
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