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Chemical modification of fluorinated self‐assembled monolayer surfaces using low‐energy ion beams for halogen and pseudohalogen transfer
Author(s) -
Shen Jianwei,
Grill Verena,
Evans Chris,
Cooks R. Graham
Publication year - 1999
Publication title -
journal of mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1076-5174
DOI - 10.1002/(sici)1096-9888(199904)34:4<354::aid-jms782>3.0.co;2-4
Subject(s) - chemistry , halogen , fluorocarbon , fluorine , reactivity (psychology) , monolayer , atom (system on chip) , ion , thermochemistry , surface modification , sputtering , crystallography , organic chemistry , nanotechnology , thin film , biochemistry , alkyl , medicine , alternative medicine , materials science , pathology , computer science , embedded system
Isocyanatosilane‐derived cations, Si(NCO) n + , ( n =1–4)were mass‐selected and reacted with fluorinatedself‐assembled monolayer (F‐SAM) surfaces atlow collision energy (<100 eV). Examination of thescattered products revealed a variety of reactions from simplefluorine atom abstraction (e.g. formation of SiF + ) to halogen–pseudohalogen exchange products(e.g. formation of SiF(NCO) 2 + and SiF 2 (NCO) + fromSi(NCO) 3 + ). Bare Si + • reacts predominantly by singleF‐atom abstraction, but small amounts of SiF 2 + • and SiF 3 + were also observed. The correlation of reactivity withthermochemistry and the role of the electronic configuration ofprojectile ions in multiple F‐atom abstraction processes arediscussed. Chemical modification of the F‐SAM surface itselfwas shown to be a consequence of the ion–surface collisions.For example, in situ Xe + • chemical sputtering analysis of F‐SAM surfaces exposed toSi(NCO) n + ion beambombardment revealed the presence of CF 2 NCO + ( m / z 92). This result suggests thatNCO groups are incorporated into the fluorocarbon chains at thesurface, probably via a pseudohalogen‐by‐halogenexchange mechanism. Surface modification was also achieved using thedicyanatochloromethyl cation, C(CN) 2 Cl + . Prolonged reactive collisions of C(CN) 2 Cl + upon a F‐SAM surface led to theincorporation of both chlorine atom and cyanato groups into thesurface, and these were released as CF 2 CN + ( m / z 76) and CF 2 Cl + ( m / z 85) on Xe + • sputtering analysis. Isotopic labeling experimentsconfirmed Cl substitution into the surface fluorocarbon chains.Copyright © 1999 John Wiley & Sons, Ltd.