For the study of trace elements or isotopic analysis in geology, the high sensitivity and lack of background in SIMS makes it an extremely important technique. The ability to detect the whole periodic table including light elements and distinguish between isotopes sets SIMS apart from techniques like EDS. While traditional SIMS instruments can be limited in their spacial resolution and impose constrains on sample size and mounting options, the high spacial resolution of FIB-SIMS and the greater flexibility in sample mounting makes it an ideal technique. The combination of the V500's Thru-Field extraction and high transmission spectrometer lead to high sensitivity geological analyses at spacial resolutions unachievable on other instruments.
User story 1: Lithium mapping in mica
Researchers from the Universities of Cambridge and Glasgow along with Carl Zeiss have used the V500 the map the distribution of lithium in mica, showing off feature sizes in the range tens of nanometers!
Figure 1. reproduced from Ball, M. R.; Taylor, R. J. M.; Einsle, J. F.; Khanom, F.; Guillermier, C.; Harrison, R. J. Beilstein J. Nanotechnol. 2020, 11, 1504–1515. doi:10.3762/bjnano.11.133 under creative commons license 4.0
Figure 1 a) shows a large scale BSE image of the mica sample. The SEM-EDS images of the same region in b) and c) show that lithium cannot be detected above the background level. The SIMS images from the V500 in d) and e) show that not only can lithium be detected easily, but both isotopes can be separated and both signals show features in the tens of nanometers range.
User story 2: Isotope ratio analysis
The same researchers have also used the V500 to investigate isotopic segregation in both spodumene and biotite mica.
Figure 2. reproduced from Ball, M. R.; Taylor, R. J. M.; Einsle, J. F.; Khanom, F.; Guillermier, C.; Harrison, R. J. Beilstein J. Nanotechnol. 2020, 11, 1504–1515. doi:10.3762/bjnano.11.133 under creative commons license 4.0
Figure 2 a) shows the deformed cleavage planes parallel to the c-axis in the mica sample. The variation in δ Li along the green line is shown in b). The variation in isotope ratio is too large to be explained by statistical variation and hints at geological variation as the cause. Further study is required to determine the true cause.
Read the latest FIB-SIMS publications on geology here.