Surface modification using a commercial triple quadrupole mass spectrometer

We report instrumental modifications to a commercial mass spectrometer that allow surface modification experiments to be performed using low-energy (e lectronvolt range) mass-selected ion beams. The design of the detector hous ing allows placement of the surface on the ion optical axis and some distan ce beyond the off-axis detector, Manipulation of the potentials applied to the final lens, detector housing, conversion dynode, and electron multiplie r 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 anal ysis of the modified surface is performed using a home-built multisector ma ss spectrometer, The ability to modify organic thin films is demonstrated b y a number of soft landing and surface modification experiments including ( i) soft landing of (CH3)(2)SiNCS+ ions formed from trimethylsilyl isothiocy anate upon a fluorinated self-assembled monolayer CF-SAM) surface, (ii) sof t landing and dissociative soft landing of the pseudomolecular cation of tr iphenylpyrylium tetrafluoroborate, viz, the triphenylpyrylium cation, upon an F-SAM surface, (iii) dissociative soft landing of (ClCH2)-Cl-35(CH3)(2)S iOSi(CH3)(2)(+) formed from 1,3-bis(chloromethyl)disiloxane upon an F-SAM s urface, (iv) surface passivation by reaction of the trimethylsilyl cation, Si(CH3)(3)(+), With a hydroxy-terminated self-assembled monolayer (OH-SAM), and (v) transhalogenation by reaction of CCl3+ (m/z 119) with an F-SAM sur face.