Secondary NanoSIMS

The Mattauch-Herzoggeometry (Fig. 3.20) enables detection of several masses simultaneously and is, therefore, ideal for scanning instruments [3.49]. Up to five detectors are adjusted mechanically to locations in the detection plane, and thus to masses of interest. Because of this it is possible to detect, e. g., all isotopes of one element simultaneously in a certain mass range. Also fast, sensitive, and precise measurements of the distributions of different isotopes are feasible. This enables calculation of isotope ratios of small particles visible in the image. The only commercial instrument of this type (Cameca Nanosims 50) uses an ion gun of coaxial optical design, and secondary ion extraction the lateral resolution is 50 nm. 

Another interesting suite of approaches that undoubtedly wiU be further developed employs SIMS—secondary isotope mass spectrometry (also know as multiple-isotope imaging mass spectrometry (MIMS)). Orphan et al. (2001) applied FISH—SIMS or fluorescent in situ hybridization SIMS to detect isotopicaUy Ught carbon in archaeal ceUs, identifying the Archaea by FISH and using SIMS to quantify the isotopic composition of individual ceUs by ion microprobe. Finzi et al. (2006) applied nanoSIMS to visualize uptake of N2 and C02 by individual ceUs of a... 

The name, nanoSIMS 50, stands for a new-generation SIMS instrument. The unique feature of the instrument is that it combines high sensitivity with a high lateral resolution of 50 nm when operated with the Cs primary beam. This is achieved by using a specific design of ion optics where the primary and secondary ion optics are coaxial and the primary beam hits the sample surface at an angle of 90°. Compared to the old SIMS, the transmission of the new instrument for secondary ions is a factor of -20-30 better in typical measurement conditions. 

Figure 1.5 spatial distribution maps collected at four different depths (images A-D) on a nanoSIMS 50 instrument. These were recorded from the secondary ions... 

In this chapter, the application of secondary ion mass spectrometry (SIMS) techniques, and in particular of time-of-flight secondary ion mass spectrometry (ToF-SIMS) and nanoscale secondary ion mass spectrometry (NanoSIMS), to polymer surface characterization is presented, with attention focused especially on polymer blends and interfaces. 

NanoSIMS is nanoscale secondary ion mass spectrometry technique that allows precise, spatially explicit, elemental and isotopic analysis down to 50 nm resolution [155]. When working in dynamic conditions, NanoSIMS analysis is a destructive process that involves the continuous bombardment of a sample with an energetic ( 16 keV) ion beam (either a Cs" " or O" " primary beam to enhance negative or positive ion formation, respectively), which results in sputtering of the upper sample surface and the consequent liberation of secondary ions. 

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