Low energy ion /surface reactive scattering at self -assembled monolayer surfaces and selective chemical modification of surfaces

Jianwei Shen, Purdue University

Abstract

Two important aspects of low energy ion/surface collisions, ion/surface reactions and surface modification, were investigated. Collisions of polyatomic ions with F-SAM surfaces led to observation of single or multiple fluorine atom abstraction products, along with other scattered ionic products. Free radical reactivity of distonic ions in C-F bond cleavage was also demonstrated. The reactivities of these and other ions in C-F bond cleavage were evaluated by independent examination of the modified surface. Ion/surface reactions and chemical sputtering were applied to probe the structures of surface adsorbates. Analysis of model surfaces (i.e. SAM surfaces made from 2- or 4-chlorobenzyl mercaptans), using ion/surface reactions and chemical sputtering, showed distinctive features which are associated with the adsorbate chemical structure. Transhalogenation was used to incorporate pseudohalogen groups into F-SAM surfaces. Subsequent characterization by xenon ion chemical sputtering of surfaces bombarded by the Si(NCO)n+ or C(CN) 2C1n+ ion beams suggests that selective incorporation of functional groups e.g. NCO and CN into the F-SAM surfaces was achieved. Surface modification was also achieved by soft-landing of ions into both hydrocarbon and fluorocarbon SAM surfaces. Dissociation accompanying soft-landing was characterized. It was found that fragmentation occurs primarily during the deposition but not the release process. Chemical modification of surfaces was pursued by reactions of cations ( i.e. C6H5+) with 11-MUA (NH 4+-OOC(CH2)10-S-Au) SAM surfaces. TOF-SIMS and Xe+. chemical sputtering analysis of the modified surfaces indicate that intact phenyl ions are covalently bound to the alkyl chains. The possible reaction mechanism and the potential applications of the modified surfaces are discussed.

Degree

Ph.D.

Advisors

Cooks, Purdue University.

Subject Area

Analytical chemistry

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