Application Example

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IntroductionThe TOF-SIMS analyser detects the secondary ions emitted from a specimen during FIB milling (no additional ionisation source is necessary). These secondary ions are focused and transferred to the TOF-SIMS analyser by the TOF ion optics system. In the TOF-SIMS analyser, the ions are separated according to their time of flight and detected. The SEM part of the system is usually used for easy navigation on the sample and, if necessary, for charge compensation.

ApplicationsThe FIB - induced secondary ions are generated, frame by frame, from an increasing depth in the specimen. Therefore, their analysis is an effective way to determine the chemical composition of the specimen and its variation with depth (depth profiling). An example of an oxygen gradient in a CrN film on a WC-Co substrate is given in Fig 2. The user not only obtains the depth profile and the total spectrum, which is integrated from all the frames, but may also generate

The unique combination of an FIB-SEM system from TESCAN and a Time-of-Flight (TOF) Secondary Ion Mass Spectrometer (SIMS) from TOFWERK represents a novel and cost-effective solution for material analysis. The user of the system is provided with information on the material composition (including light elements) and distribution of individual elements in the analysed volume. The integrated analyser can detect various trace elements, often at concentrations of a few ppm, and distinguish individual isotopes.

The cutting-edge analytical solution

LYRA3 FIB-SEM with integratedTOF-SIMS analyser

c Fig. 1: LYRA3 with TOF-SIMS

c Fig. 2: An example of (a) a crater after TOF-SIMS analysis (analysed volume), (b) depth profile with an element distribution map (side view)

of oxygen and (c) spectra from the specimen (negative ions were detected)

c Fig. 3: Volume selection – an illustration

2a 2b 2c

spectra from selected regions (e.g. a few frames) and compare them - the regions can be specified using the Top view and Side view cross-section images (Fig. 3). Another significant advantage of TOF-SIMS is that the interaction volume of the secondary ions is smaller than the interaction volume of X-rays generated by the electron beam. Therefore, TOF-SIMS offers a considerably better resolution than energy / wavelength dispersive X-ray spectroscopy (EDS / WDS). Moreover, its detection limit is incomparably better. For example, boron in silicon can be detected at a concentration of a few ppm. Thus, TOF-SIMS was chosen for the detection and mapping of secondary phase Fe / Cr particles, with dimensions of

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Application Example The cutting-edge analytical solution - LYRA3 FIB-SEM with integrated TOF-SIMS analyser

only hundreds of nm, in a Zircaloy sample.The chromium isotope with the highest abundance is 52Cr+. Because the amount of chromium in the sample is very small, the 52Cr+ isotope was selected for visualizing the particles in the cross-section images (Fig. 4 a-b). If the signal was only integrated from the regions where a particle was found, the visualization becomes much clearer (Fig. 4 c-d). The particle can be also compared with the FIB secondary electron image (Fig. 4 e), which can be recorded from each analysed frame simultaneously with the analysis - as in the previous example, a spectrum can be generated from the particle (Fig. 4 f).The third example of a TOF-SIMS application in material science is the analysis of elbaite (sodium lithium aluminum boro-silicate). Among other elements, it was possible to detect both Li isotopes (Fig. 5). Lithium is a light element which is difficult to detect by other electron microscopy related techniques.

ConclusionThe powerful combination of a TESCAN FIB-SEM with TOF-SIMS extends the frontiers of the analytical methods available in the field of electron microscopy. The integrated TOF-SIMS enables 3D chemical mapping, the detection of light elements and distinguishes individual isotopes.

� AcknowledgementsMany thanks belongs to Mr. Michal Šíma from

SHM, s.r.o. for providing CrN/WC-Co samples

and information.063124.

c Fig. 4: (a) Top view of 52Cr+ distribution generated from all analysed frames, (b) Side view of 52Cr+ distribution generated from the whole area of 16 μm2, (c) Top view of 52Cr+ distribution

generated only from the 32 frames in which the particle was detected, (d) Side view of 52Cr+ distribution generated only from the region in which the particle was found, (e) FIB

secondary electron image, (f) Comparison of the total spectrum and the spectrum from

the particle (positive ions were detected).

f Fig. 5: Elbaite spectrum (oxygen has better

signal in negative ion mode)

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