Variation of yield with thickness in SIMS and PDMS: Measurements of secondary ion emission from organized molecular films

Bolbach, G.; Beavis, Ronald C.; Negra, S. Della; Deprun, C.; Ens, Werner; LeBeyec, Y.; Main, D. E.; Schueler, B.; Standing, K. G.

doi:10.1016/0168-583x(88)90082-1

Cited by 37 publications

(13 citation statements)

References 35 publications

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“…25 LB films grown on reactive substrates show an increase in (M H yield with increasing thickness whereas those grown on non-reactive substrates show a decrease in yield with thickness. The effect of the substrate becomes small when the sample reaches a thickness of ¾10 monolayers.…”

Section: Using 21 Kev Csmentioning

confidence: 81%

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Mechanisms of secondary ion emission from self‐assembled monolayers and multilayers

Wong

Lockyer

Vickerman

2005

Surface & Interface Analysis

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Alkanethiol self-assembled monolayers/multilayers (SAMs) have been applied as model organic systems with which to investigate secondary ion formation and emission processes during kiloelectronvolt ion bombardment. Self-assembled monolayer and multilayer films of 11-mercaptoundecanoic acid capped with 1-dodecanethiol were prepared on gold-coated substrates. Samples with varying number of thiolate layers were studied using static secondary ion mass spectrometry to investigate the origin of molecular secondary ions and the influence of surface chemistry and structure. The nature of the thiolate bonding affects the type and abundance of the observed ions. The intensity of atomic and cluster ions derived from the substrate decreases exponentially with increasing number of thiolate overlayers because of losses in transmission through the organic overlayers. Intact molecular and cluster ions can escape from >100Å below the surface of these structures. The variation of molecular-ion yields with multilayer thickness suggests that a significant proportion of molecular ions originate from subsurface thiolate layers. The detection of ions comprised species from the substrate or bottom of the multilayer associated with species from the top layer supports the view that chemical association at or near the surface is a viable mechanism of formation for molecular secondary ions.

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Section: Using 21 Kev Csmentioning

confidence: 81%

“…This is consistent with previous observations and can be attributed to chemical effects such as changes in ionisation probability or surface binding energy. 25 A systematic investigation of the variation in Au x x D 1-3) intensity with number of layers is presented in Fig. 4.…”

Section: Ddt-capped Mua Multilayersmentioning

confidence: 99%

Mechanisms of secondary ion emission from self‐assembled monolayers and multilayers

Wong

Lockyer

Vickerman

2005

Surface & Interface Analysis

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“…Thus, it can be concluded that the yield variations are almost identical for all the ions; after a fairly constant variation down to around 50 µg · cm −2 (or around 250 nm), a decrease is observed down to around 5 µg · cm −2 , and the decrease is then more pronounced towards the lowest values. If this final decrease corresponds to a thickness range below the emission depth (several tens of nm22), then the transition zone (25–250 nm) could be indicative of a heterogeneous coverage of the dried solution onto such a substrate.…”

Section: Resultsmentioning

confidence: 99%

Assessment of the plasma desorption time‐of‐flight mass spectrometry technique for pesticide adsorption and degradation on ‘as‐received’ treated soil samples

Thomas

Nsouli²,

Darwish

et al. 2005

Rapid Comm Mass Spectrometry

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The assessment of the plasma desorption time-of-flight mass spectrometry (PD-TOFMS) technique as a tool for direct characterization of pesticides adsorbed on agricultural soil is made for the first time in this study. Pellets of soils impregnated by solutions of three pesticides, namely norflurazon, malathion and oxyfluorfen, as well as deposits of these solutions onto aluminum surfaces, were investigated to this end. The yield values of the most characteristic peaks of the negative ion mass spectra were used to determine both the lowest concentrations detected on soils and limits of detection from thin films. The lowest values on soils are for malathion (1000 ppm range), and the largest for norflurazon (20 000 ppm), which is close to the limit of detection (LOD) found for the pesticide on the aluminum substrate ($0.2 mg Á cm À2 ). Different behaviors were observed as a function of time of storage in the ambient atmosphere or under vacuum; norflurazon adsorbed on soil exhibited high stability for a long period of time, and a rapid degradation of malathion with the elapsed time was clearly observed. The behavior of oxyfluorfen was also investigated but segregation processes seem to occur after several days. Although by far less sensitive than conventional methods based on extraction processes and used for real-world analytical applications, this technique is well suited to the study of the transformations occurring at the sample surface. A discussion is presented of the future prospects of such experiments in degradation studies.

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“…The observation of metal atoms ejecting in the presence of a thick organic layer is not unprecedented [35]. Bolbach et al [36] deposited Cd stearate Langmuir-Blodgett layers on Au and Ag substrates and measured the substrate ion signal due to 21 keV Cs bombardment as a function of coverage. They found that there is a measurable Ag ion signal to 8 layers or about 200 Å .…”

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confidence: 99%

Surface Sensitivity in Cluster-Ion-Induced Sputtering

et al. 2006

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The ion beam-induced removal of thin water ice films condensed onto Ag and bombarded by energetic Au, Au2, Au3, and C60 projectiles is examined both experimentally and with molecular dynamics computer simulations. For water overlayers of thicknesses greater than 10 A, the yields of sputtered Ag+ secondary ions decay exponentially with increasing ice thickness, revealing characteristic decay lengths of 24, 20, 18, and 7.0 A, respectively. It is shown that these values manifest the characteristic depths of projectile energy loss, rather than escape depths of the sputtered Ag atoms through the water ice overlayer. Computer simulations show that the mechanism of ejection involves the sweeping away of overlayer water molecules, allowing for an unimpeded escape of ejected Ag atoms. The relevance of these data with respect to surface sensitivity in secondary ion mass spectrometry is discussed.

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Variation of yield with thickness in SIMS and PDMS: Measurements of secondary ion emission from organized molecular films

Cited by 37 publications

References 35 publications

Mechanisms of secondary ion emission from self‐assembled monolayers and multilayers

Mechanisms of secondary ion emission from self‐assembled monolayers and multilayers

Assessment of the plasma desorption time‐of‐flight mass spectrometry technique for pesticide adsorption and degradation on ‘as‐received’ treated soil samples

Surface Sensitivity in Cluster-Ion-Induced Sputtering

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