Sample Preparation
Sample preparation is VERY IMPORTANT for a successful SIMS measurement. Here, we summarise some of the requirements that every sample, which is to be analysed by the NanoSIMS, must meet.
No Outgassing
The NanoSIMS operates at room temperature under ultra high vacuum (10−9 - 10−11 mbar). Hence, your sample must not outgass. Please make sure that no part of your sample contains any fluid as outgassing could cause a serious damage to the machine.
Flat Surface
A rough surface may cause sample charging and/or artificially enhance ion yields at peaks and troughs, resulting in inaccurate results. Thus, your sample needs to be microtomed or polished to a final grit of < 1 μm (ideally < 0.25 μm). The polished sample should not be bevelled, sloping or rounded at the edges. Please confirm that your sample is adequately polished by examining it under a microscope in the end.
Mount Dimensions
Your sample will be mounted on a designated holder for a NanoSIMS measurement. We offer three kinds of holders, as shown below.
- 1 × 1" hole
- 5 × 10-mm holes
- 1 × 1" hole
- 2 × 0.5" holes
- 2 × 10-mm holes
- 8 × 10-mm holes
Your sample must be of a correct diameter with a tolerance of + 0.2 mm and − 0.5 mm. The height should be 4 - 6 mm. Each experiment is generally limited to one holder, so please plan ahead if you have multiple samples; you may want to distribute them to small (0.5" or 10-mm) mounts or combine and embed them together in a 1"-mount.
Embedding
Embedding depends on application. For grain samples (hard and irregular-shaped), we recommend you embed your sample in high vacuum epoxy resin or indium. For flat samples (e.g. a microtomed surface), we will fixate it to an aluminium cylinder. For biological samples, please contact us as they generally require special considerations and techniques for embedding. Please ensure that the embedded sample meets the above dimension requirement.
Standard
If your measurement involves trace or uncommon elements, we will require a standard with known isotopic compositions. The standard should:
- be homogeneous
- match the mineralogical and chemical compositions with your sample
- be embedded in the same mount as your sample (ideally within < 1 cm from your sample).
SEM/Optical Mapping
The NanoSIMS has a limited field of view. Therefore, we need an optical or SEM map of the whole sample at a reasonable magnification, with the area of interest, being marked.