Sample requirements

Information on specimen holders, photographs and navigation

The Cameca 4f, 7f and 1270 accept the same type of specimen holder. The specimen should be 24 - 24.5mm in diameter and less than 5mm thick. The area that can be analysed is within ~9mm of the centre, although this is reduced to +/- 5mm from the centre for high precision isotopic analysis. If the mount is prepared using Epoxy resin, then the surface should be bubble-free, flat across the whole diameter and have minimal polishing relief.

Photographs and navigation

Good, low magnification, reflected light photographs are essential for navigating around the sample. The inclined reflected light optical microscope on the Cameca 4f has a 1.7mm field of view. SEM photographs may be of use, but these should be at low magnification and include a secondary electron image. The closest similarity to the Cameca optics is achieved using reversed bias secondary electron images where the sample relief is enhanced. Backscatter images are of little use for navigation.

It is essential that if the samples are mounted in epoxy resin, the SEM imaging does not produce a raster trench around each grain. This epoxy damage is caused by high current and slow scan rates often used for CL imaging. If publication-quality images are needed, then these are best done after the SIMS analysis. For the SIMS work, we just need a navigation aid.

Sample preparation

All epoxy resins degas to a greater or lesser extent and will contribute to the H background in the instrument. They should be used sparingly, and solid grain mounts should be as thin as possible (5mm thickness is ideal).

We recommend the use of Epothin, SpeciFix-20 or EpoFix for SIMS analysis.

Insulating samples need to be coated with a thin layer of Au (10-30nm) or C (electron probe analysis). Conducting epoxy resins (Ag loaded) and conducting paints (Ag DAG or Aquadag) may be used to obtain a conducting path from the sample to the specimen holder.

For certain types of work, sample preparation is extremely important. Polishing compounds will contaminate the sample in Al (alumina polishing), Si (Syton polishing), B (diamond polishing compounds), Pb (Pb laps), C (from everywhere) and inevitably, Na.

Please read the guidance on sample preparation under the Epoxy resins section of the website:

Epoxy resins