ToF-SIMS Sample Preparation and Handling Instructions
Some general rules:
Avoid contaminating the surfaces of the samples by excessive handling, scratching or contact with other surfaces.
- Cleaning solvents such as hexane, isopropyl alcohol, chloroform and acetone can be used, but these may leave residues and/or alter the surface being investigated.
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Samples need to be able to withstand ultra high vacuum conditions. Pumping time for the airlock and main chamber will depend on the size and form of the sample. Samples with a large surface area or with volatile components should ideally be dried, and pumped down prior to insertion.
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Health and safety: MSDS sheets and any relevant handling information should be supplied with all samples where appropriate.
In order to help avoid contamination do NOT use:
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Plastic containers (other than polystyrene petri-dishes) for sample preparation or storage.
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Powdered or plastic gloves for handling (polyethylene is acceptable).
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Tweezers or other tools made of plastic.
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Plastic bags for sample storage.
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Standard laboratory solvents (high purity chemicals are required).
Powder samples
Powder samples can be mounted in a number of ways, preferred methods include:
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Pressing into Indium where high purity Indium is essential.
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Deposition from slurry onto a suitable substrate.
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Forming a sample disc by pressing, although this may require a long 'pump-down' so supply the sample well ahead of experimental time.
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Sprinkling on adhesive tape (the tape has to be free of contamination and chemically distinct or compatible with the samples).
We have a number of specialist mounting methods in house. Get in touch if you have particularly challenging samples and we'd be happy to advise/help.
Volatile Samples
Materials (with components) that would normally pump away in a vacuum chamber at room temperature can often be analysed using the cooling facilities (cryo-stage) to the airlock and analysis chamber (down to -100°C).
Biological samples and other samples that may be affected by vacuum conditions
In a number of cases these can be cooled sufficiently to minimise the effects of the vacuum on the sample but a discussion with operational personnel may be required.
Solvent Use
Always use clean solvents of high purity if possible. We use AnalaR grade as supplied by VWR . If high purity solvents are not available the sample should be rinsed in high purity hexane after the use of impure solvents. In case of doubt we can on request check your samples or solvents for contamination prior to full analysis. Avoid any contact of solvents or sample with plastics throughout, this is especially important for SIMS analysis. Only use poly-ethylene (PE) gloves, always avoid the use of nitrile gloves.
Substrate cleaning
Sonicate for 10 min. in dichloromethane (standard laboratory grade should suffice). Further Sonication for 10 min. in hexane (AnalaR grade or similar) and final sonication for 10 min. in chloroform (AnalaR grade or similar).
Containers
Do not use plastic containers other than petri-dishes made of polystyrene. In case of doubt use glass containers for sample preparation cleaned with the above method or alternatively aluminium foil tends to be clean enough for most purposes and can be used for sample packaging. Ensure that the outer part of the roll is not used. We find that the Wilko brand (from Wilkinson shops) is especially clean. If none of the above options is feasible, an unbleached, brown envelope can be used.
Size
Thin, flat squares of dimension between 10 - 12 mm and thickness up to ca. 5mm are ideal and allow mounting of up to 15 samples at a time. Other sample sizes up to a maximum of 10 cm are possible where thickness restrictions apply, please
contact us to discuss sample requirements.
Topography
As the time-of-flight of secondary ions formed carry the required mass information, any surface topography will degrade mass resolution, therefore only fairly flat areas can thus be analysed well. A number of work-arounds can often help and, in case of doubt, please contact us