TOF-SIMS with Argon Gas Cluster Ion Beams: A Comparison with C₆₀⁺

Abstract

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) is an established technique for the characterization of solid sample surfaces. The introduction of polyatomic ion beams, such as C(60), has provided the associated ability to perform molecular depth-profiling and 3D molecular imaging. However, not all samples perform equally under C(60) bombardment, and it is probably naïve to think that there will be an ion beam that will be applicable in all situations. It is therefore important to explore the potential of other candidates. A systematic study of the suitability of argon gas cluster ion beams (Ar-GCIBs) of general composition Ar(n)(+), where n = 60-3000, as primary particles in TOF-SIMS analysis has been performed. We have assessed the potential of the Ar-GCIBs for molecular depth-profiling in terms of damage accumulation and sputter rate and also as analysis beams where spectral quality and secondary ion yields are considered. We present results with direct comparison with C(60) ions on the same sample in the same instrument on polymer, polymer additive, and biomolecular samples, including lipids and small peptides. Large argon clusters show reduced damage accumulation compared with C(60) with an approximately constant sputter rate as a function of Ar cluster size. Further, on some samples, large argon clusters produce changes in the mass spectra indicative of a more gentle ejection mechanism. However, there also appears to be a reduction in the ionization of secondary species as the size of the Ar cluster increases.

New mass spectrometry techniques for studying physical chemistry of atmospheric heterogeneous processes

“…This property of cluster beam bombardment is a key to accurate depth profiling using ion beams [154,162,163] and will be discussed later. Rabbani et al compared the performance of C 60 + and large, singly charged argon clusters for depth profiling using SIMS [165]. The results demonstrate that, in comparison with C 60 , surface bombardment with large argon clusters results in gentler sputtering and reduces surface damage.…”

Latest applications of 3D ToF-SIMS bio-imaging

“…47,48 Rabbani et al reported improved molecular ion signal levels from lipid and neuropeptide standard samples after continued bombardment with 20 kV Ar cluster beams. 49 Improved molecular signal levels compared with C 60 bombardment for lipid species in cell and tumor samples have been reported 50 and most recently Bich and co-workers showed persistent lipid signal when a depth profile was performed through a rat brain section that was sliced at 14 lm thickness and analyzed after freeze drying when the tissue thickness had been reduced to approximately 1.2 lm. 51 The implication is that these new beams will offer improved performance in a wide range of 3D biological imaging experiments.…”

Lignification of ray parenchyma cells (RPCs) in the xylem of Phellodendron amurense Rupr.: quantitative and structural investigation by TOF-SIMS and thioacidolysis of laser microdissection cuts of RPCs

“…Hereafter, the results obtained from ROIs will be compared. The relative amount of lignin type ions can be well quantified based on the secondary cellulose ions (Rabbani et al 2011;Zheng et al 2014a), despite the limitations of this technique due to the ionization efficiency and the so-called matrix effect. In the TOF-SIMS measurements, secondary ions derived from lignin are generated as a result of fragmentation of lignin. )…”