C60 molecular depth profiling of a model polymer

Szakal, Christopher; Sun, Shilong; Wucher, A.; Winograd, Nicholas

doi:10.1016/j.apsusc.2004.03.113

Cited by 67 publications

(84 citation statements)

References 4 publications

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“…For example, these sources can be focused onto the sample with a probe size about 1 micron, allowing greatly improved molecule-specific imaging experiments. The high secondary ion yield associated with the cluster/solid interaction also allows for molecular depth profiling studies without the accompanying damage accumulation normally associated with atomic bombardment [7][8][9][10][11][12][13][14][15][16][17].…”

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confidence: 99%

Energetic ion bombardment of Ag surfaces by C₆₀⁺ and Ga⁺ projectiles

Sun

Szakal

Winograd

et al. 2005

J. Am. Soc. Mass Spectrom.

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The ion bombardment-induced release of particles from a metal surface is investigated using energetic fullerene cluster ions as projectiles. The total sputter yield as well as partial yields of neutral and charged monomers and clusters leaving the surface are measured and compared with corresponding data obtained with atomic projectile ions of similar impact kinetic energy. It is found that all yields are enhanced by about one order of magnitude under bombardment with the C 60 ϩ cluster projectiles compared with Ga ϩ ions. In contrast, the electronic excitation processes determining the secondary ion formation probability are unaffected. The kinetic energy spectra of sputtered particles exhibit characteristic differences which reflect the largely different nature of the sputtering process for both types of projectiles. In particular, it is found that under C 60 ϩ impact (1) the energy spectrum of sputtered atoms peaks at significantly lower kinetic energies than for Ga ϩ bombardment and (2) the velocity spectra of monomers and dimers are virtually identical, a finding which is in pronounced contrast to all published data obtained for atomic projectiles. T he elucidation of the mechanism of interaction of energetic polyatomic or cluster ions with surfaces is of current interest since these projectiles are now being extensively employed as desorption probes in secondary ion mass spectrometry (SIMS) experiments [1,2]. Because of their propensity to produce higher molecular ion signals than corresponding atomic ions and the emergence of commercially available C 60 ϩ [3,4] and Au 3 ϩ [5, 6] ion guns, applications have expanded dramatically. For example, these sources can be focused onto the sample with a probe size about 1 micron, allowing greatly improved molecule-specific imaging experiments. The high secondary ion yield associated with the cluster/solid interaction also allows for molecular depth profiling studies without the accompanying damage accumulation normally associated with atomic bombardment [7][8][9][10][11][12][13][14][15][16][17].The mechanisms associated with the observed secondary ion yield enhancement are not yet clear, although details are emerging quickly. A basic question that must be resolved is to determine whether the yield enhancement occurs as a consequence of increased ionization efficiency, or is due to more effective sputtering in the neutral desorption channel. There is mixed information about this point. For In and Ag surfaces, for example, it has been shown that the enhanced secondary ion yield under SF m ϩ bombardment (m ϭ 1-5) largely arises from the enhanced ionization efficiency attributable to implanted F atoms [18]. For organic systems, however, very high removal rates of neutral species have been reported [2], obviating the need to invoke enhancement of the secondary ionization probability. Most recently, yields and velocity distributions were measured for In and In 2 sputtered from In surfaces bombarded with Au ϩ , Au 2 ϩ , and Au 3 ϩ [19]. Although these experiments do not ad...

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confidence: 99%

Energetic ion bombardment of Ag surfaces by C₆₀⁺ and Ga⁺ projectiles

Sun

Szakal

Winograd

et al. 2005

J. Am. Soc. Mass Spectrom.

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“…There has been a recent flurry of interest in utilizing energetic buckminsterfullerene (C 60 ) molecules [1][2][3][4][5][6][7][8][9][10][11][12] for surface characterization in time-of-flight secondary ion mass spectrometry (SIMS) experiments. 13 For these experiments, C 60 + ions are accelerated to between 10 and 20 keV, pulsed, and focused onto a target causing desorption of atoms and molecules from the near-surface region.…”

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confidence: 99%

Microscopic Insights into the Sputtering of Ag{111} Induced by C₆₀ and Ga Bombardment

et al. 2004

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Molecular dynamics computer simulations have been utilized to compare the differences in the mechanism of sputtering of Ag{111} by kiloelectronvolt Ga and C 60 projectiles. The calculated kinetic energy distributions of Ag monomers and Ag 2 dimers compare favorably with experimental results. The damage caused by the C 60 particle left in the sample is less than the depth of material that the next impinging C 60 particle would remove, thus supporting the preliminary experimental observations that molecular depth profiling is possible with C 60 projectile beams.

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“…S econdary ion mass spectrometry (SIMS) has become a powerful analysis tool for depth profiling or chemical mapping of organic and biological systems [1][2][3][4][5]. One such application has been onedimensional depth profiling of polymer films and multilayers, which has provided a significant driving force for growth in experimental and theoretical polymer physics over the past 20 years [6].…”

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confidence: 99%