SAMPLE PREPARATION: Imaging your samples before WiscSIMS analysis
Careful imaging of your polished mount is essential for analysis. You will have a 500 x 400 micron view of your sample while it is in the SIMS, and it can be difficult to orient yourself with such a small field of view. Thus, it is recommended that you have at least: 1) a single image of the entire "sweet spot"; 2) high magnification images of your entire analytical target (for 10-micron spot analyses, it is useful to have image maps where 1 pixel ~ 1 micron). If you have a large analytical target, you may need to create a large sample map by digitally stitching multiple high-magnification images together with Adobe Illustrator, FIJI, or Microsoft ICE.
Recall that non-conductive samples will be gold- or carbon-coated for WiscSIMS analysis. As a result, you will only be able to see cracks, scratches, and some grain boundaries with the WiscSIMS camera. For users that are targeting geochemical features that have been imaged by other means (e.g. SEM, fluorescence microscope), it will be helpful to have both the geochemical imaging as well as optical imaging of the gold-goated surface.
You can coat your sample at UW if necessary, otherwise a ~30 nm coat is appropriate for most applications. Note: If you plan to coat your samples before arriving in Madison (e.g. for SEM analysis), we recommend that you clean and degas your mounts before coating to prevent problems under the high vacuum in the instrument. To clean your epoxy mount (mostly of fingerprint oils), we sonicate each mount for 30 seconds in ethanol then again for 30 seconds in DI water. If possible we move the cleaned mount, using gloves, to a vacuum-oven to dry for 3+ hours. It's a good idea to place new mounts under high-vacuum (10^-6 Torr) overnight to degas the epoxy. If you cannot clean or degas your sample before coating, we will remove the coating to perform these steps when you arrive for your analysis session.
Thin slices of biological samples (<few μm) placed flat on a Si-wafer can be analyzed without surface coating.
Print out your sample images and bring them along for your analytical session. For large analytical targets like a cm-long traverse, it may be necessary to print the traverse on 3 or more pages (with some overlap included on each page). In this case, consider organizing and labelling these image maps in a 3-ring binder.
Imaging examples and tutorials from WiscSIMS:
- Sample imaging: selecting suitable domains for SIMS analysis (pdf)
- Sample imaging: Imagery-correlated high-precision stable isotope analysis (pdf)
- Sample imaging: Sub-one- to three-micron pits (pdf)
- Navigation on difficult samples: mapping of sandstones (pdf)
- Point logger: precise aiming in difficult samples (pdf)
If your project has been aproved by the lab, you're now ready to schedule an analysis session at WiscSIMS! See the "Access Guide" page for detailed instructions on how to proceed.
Following WiscSIMS anlaysis: