Surface Modification Using a Commercial Triple Quadrupole Mass Spectrometer

• Published in: Analytical chemistry (Washington) 2000-12, Vol.72 (23), p.5798-5803
• Main Authors: Denault, Jeff W, Evans, Chris, Koch, Kim J, Cooks, R. Graham
• Format: Article
• Language: English
• Subjects: Chemistry; Exact sciences and technology; General and physical chemistry; Instruments; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; Ions; Langmuir blodgett films; Mass spectrometers and related techniques; Physics; Spectrum analysis; Surface physical chemistry
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac0005823

We report instrumental modifications to a commercial mass spectrometer that allow surface modification experiments to be performed using low-energy (electronvolt range) mass-selected ion beams. The design of the detector housing allows placement of the surface on the ion optical axis and some distance beyond the off-axis detector. Manipulation of the potentials applied to the final lens, detector housing, conversion dynode, and electron multiplier allow the ions to pass through the detector housing and impinge upon the surface without loss of the normal mode of detector operation. Ex situ analysis of the modified surface is performed using a home-built multisector mass spectrometer. The ability to modify organic thin films is demonstrated by a number of soft landing and surface modification experiments including (i) soft landing of (CH3)2SiNCS+ ions formed from trimethylsilyl isothiocyanate upon a fluorinated self-assembled monolayer (F-SAM) surface, (ii) soft landing and dissociative soft landing of the pseudomolecular cation of triphenylpyrylium tetrafluoroborate, viz. the triphenylpyrylium cation, upon an F-SAM surface, (iii) dissociative soft landing of 35ClCH2(CH3)2SiOSi(CH3)2 + formed from 1,3-bis(chloromethyl)disiloxane upon an F-SAM surface, (iv) surface passivation by reaction of the trimethylsilyl cation, Si(CH3)3 +, with a hydroxyl-terminated self-assembled monolayer (OH-SAM), and (v) transhalogenation by reaction of CCl3 + (m/z 119) with an F-SAM surface.