SAMPLE PREPARATION: Imaging your samples after WiscSIMS analysis
Following ion microprobe analysis, you will need to screen the analysis pits by SEM for aberrations like cracks or inclusions. The easiest way to do the screening is immediately following analysis and before you remove the conductive coating. After your analysis session, if you add a thin conductive coating (e.g. 30 second gold-coating at the WiscSIMS lab) to coat the pit-bottoms, you can take your sample directly to an SEM for imaging. It is possible to image pits once the coating has been removed by using Environmental Mode (low-vacuum) SEM settings, but this is not ideal.
Settings that have proven useful for imaging coated samples on the UW SEM: 15 kV beam, 40 mA current, secondary electron (SE) imaging, 4000x magnification.
Use the SEM to inspect the condition of each pit-bottom, both samples and standards. We classify the condition of each pit as either "regular", "irregular", or "borderline." These classifications are somewhat qualitative and your threshold for "irregular" may change with experience, but this process is useful for independently identifying potential outliers that may be eliminated from a published dataset.
- "Regular" pit-bottom in calcite standard grain
- "Irregular" pit-bottom, veins/cracks in calcite sample
- "Irregular" pit-bottom, voids in calcite sample