Molecular secondary particle emission from molecular overlayers under 10 keV Ar+ primary ion bombardment

Schnieders, Albert; Möllers, R.; Benninghoven, A.

doi:10.1016/s0039-6028(00)00911-0

Cited by 21 publications

(23 citation statements)

References 6 publications

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“…In the negative ion mode, the characteristic secondary ions followed similar trends to those seen in the positive ion mode (Figs 4(a) 37 This matrix effect was not observed in the positive ion depth profiles and was not evident in the negative ion depth profiles of PMAA possibly because of the visible roughness of these samples.…”

Section: Negative Ion Depth Profilessupporting

confidence: 58%

Degradation of poly(acrylates) under SF5+ primary ion bombardment studied using time-of-flight secondary ion mass spectrometry. 1. Effect of main chain and pendant methyl groups

Wagner

2005

Surf. Interface Anal.

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Polyatomic primary ions have been applied recently to the depth profiling of organic materials by secondary ion mass spectrometry (SIMS). Polyatomic primary ions offer low penetration depth and high damage removal rates in some polymers, but the relationship between polymer chemistry and degradation under polyatomic primary ion bombardment has not been studied systematically. In this study, positive and negative ion time-of-flight SIMS (ToF-SIMS) was used to measure the damage of ∼100 nm thick spin-cast poly(methyl methacrylate) (PMMA), poly(methyl acrylate) (PMA) and poly(methacrylic acid) (PMAA), films under extended (∼2 × 10 14 ions cm −2 ) 5 keV SF 5 + bombardment. These polymers were compared to determine the effect of the main chain and pendant methyl groups on their degradation under SF 5 + bombardment. The sputter rate of PMMA was approximately twice that of PMA or PMAA and the rate of damage accumulation was higher for PMA and PMAA than PMMA, suggesting that the main chain and pendant methyl groups played an important role in the degradation of these polymers under SF 5 + bombardment. These results are consistent with the literature on the thermal and radiation-induced degradation of these polymers, which show that removal of the main chain or pendant methyl groups reduces the rate of depolymerization and increases the rate of intra-or intermolecular cross-linking.

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Section: Negative Ion Depth Profilessupporting

confidence: 58%

Degradation of poly(acrylates) under SF5+ primary ion bombardment studied using time-of-flight secondary ion mass spectrometry. 1. Effect of main chain and pendant methyl groups

Wagner

2005

Surf. Interface Anal.

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“…16,17 For both negative ion depth profiles, the characteristic secondary ion intensities of the polymer rose slightly at the polymer/silicon interface, with TFAA-PHEMA showing a larger intensity increase than PHEMA. This may have been due to a substrate-related matrix effect that can increase the sputter or ionization yield of the polymer-related fragments near the silicon substrate 18 and was not observed in the positive ion depth profiles. Normalization of each spectrum in the depth profiles to its own total secondary ion intensity in the m/z D 26-200 range was used to examine the changes in relative secondary ion intensity (as opposed to absolute intensity) of the characteristic secondary ions of the polymers.…”

Section: Negative Ion Depth Profilesmentioning

confidence: 96%

Degradation of poly(acrylates) under SF5+ primary ion bombardment studied using time-of-flight secondary ion mass spectrometry. 3. Poly(hydroxyethyl methacrylate) with chemical derivatization

Wagner

2005

Surf. Interface Anal.

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Molecular depth profiling of polymers by secondary ion mass spectrometry (SIMS) has focused on the use of polyatomic primary ions due to their low penetration depth and high damage removal rates in some polymers. This study is the third in a series of systematic characterizations of the effect of polymer chemistry on degradation under polyatomic primary ion bombardment. In this study, timeof-flight SIMS (ToF-SIMS) was used to assess 5 keV SF 5 + -induced damage of ∼90 nm thick spin-cast poly(2-hydroxyethyl methacrylate) (PHEMA) and ∼130 nm thick trifluoroacetic anhydride-derivatized PHEMA (TFAA-PHEMA) films. The degradation of these polymers under extended SF 5 + bombardment (∼2 × 10 14 ions cm −2 ) was compared to determine the effect of the pendant group chemistry on their degradation. The sputter rate and ion-induced damage accumulation rate of PHEMA were similar to a poly(n-alkyl methacrylate) of similar pendant group length, suggesting that the addition of a terminal hydroxyl group to the alkyl pendant group does not markedly change the stability of poly(n-alkyl methacrylates) under SF 5 + bombardment. The sputter rate and ion-induced damage accumulation rate of TFAA-PHEMA were much higher than a poly(n-alkyl methacrylate) of similar pendant group length, suggesting that derivatization of the terminal hydroxyl group can significantly reduce degradation of the polymer under SF 5 + bombardment. This result is in good agreement with the literature on the thermal and radiation-induced degradation of fluorinated poly(alkyl methacrylates), which suggests that the electronwithdrawing fluorinated pendant group increases the probability of depolymerization.

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“…In the case of molecular ion yield enhancement, the thickness of the organic overlayer on the substrate is critical. In work by Schnieders et al [15], secondary ion yield is shown to peak at approximately one monolayer polymer cover-age and falls away as the coverage increases as a result of the changing matrix. Above one monolayer coverage, the primary ion loses more energy in the organic layer below and the organic layer furthermore prevents the efficient ejection of metal atoms from the collision cascade.…”

mentioning

confidence: 96%

“…However, molecular dynamic simulations of polyatomic ion sputtering of small organic molecules on silver substrates predict little enhancement in molecular ion yields [14]. This points to the importance of the substrate (organic versus metallic) in the use of polyatomic versus monatomic primary ion source, elucidated by the work of Schnieders et al [15], in which a high variability of secondary ion yields from a variety of substrate materials was found. In the case of molecular ion yield enhancement, the thickness of the organic overlayer on the substrate is critical.…”

mentioning

confidence: 99%

“…A large volume of work exists comparing primary ion source performance [16 -19], the effect of different substrates [15,20], and molecular dynamic simulations, considering both substrate and primary ion type [14,[21][22][23]. The goal of the present study is to compare the results of MWD and polydispersity index (PDI) determined by TOF-SIMS from a well defined poly(dimethyl siloxane) (PDMS) polymer with narrow molecular weight distribution.…”

mentioning

confidence: 99%

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Time of flight secondary ion mass spectrometric determination of molecular weight distributions of low polydispersity poly(dimethyl siloxane) with polyatomic primary ions

Wells

Moon

Gardella

2009

J. Am. Soc. Mass Spectrom.

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This work reports a comparison of oligomer and fragment ion intensities resulting from primary ion bombardment with several primary ion sources (Bi n ϩ , C 60 ϩ , and Cs ϩ ) at various energies in secondary ion mass spectrometry (SIMS). Although the use of polyatomic primary ions are of great interest due to increased secondary ion efficiency and yield, we demonstrate that monatomic primary ions result in increased oligomer ion yield for polymers prepared as submonolayer films on silver substrates. The enhancement of oligomer secondary ion yield with monatomic ions is evidence that monatomic primary ions have a shallower sampling depth than polyatomic ions, resulting from a collision cascade that is less energetic at the sample surface. The results are also consistent with a lower degree of fragmentation of the resultant secondary ions, which is observed when evaluating the fragmentation data and the spectral data. (J Am Soc Mass Spectrom 2009, 20, 1562-1566

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Molecular secondary particle emission from molecular overlayers under 10 keV Ar+ primary ion bombardment

Cited by 21 publications

References 6 publications

Degradation of poly(acrylates) under SF5+ primary ion bombardment studied using time-of-flight secondary ion mass spectrometry. 1. Effect of main chain and pendant methyl groups

Degradation of poly(acrylates) under SF5+ primary ion bombardment studied using time-of-flight secondary ion mass spectrometry. 1. Effect of main chain and pendant methyl groups

Degradation of poly(acrylates) under SF5+ primary ion bombardment studied using time-of-flight secondary ion mass spectrometry. 3. Poly(hydroxyethyl methacrylate) with chemical derivatization

Time of flight secondary ion mass spectrometric determination of molecular weight distributions of low polydispersity poly(dimethyl siloxane) with polyatomic primary ions

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