Preparation of Indium Mounts for SIMS Analysis.
specimens and for many applications it’s ideal. However, for certain analyses epoxy has
major disadvantages such as high H, C, and S contamination as well as degrading the
vacuum in the analysis chamber.
Previous studies have used low melting point alloys (e.g. Woods Metal) to mount
required. They also contain numerous elements (Bismuth, Lead, Tin and Cadmium) that
may also compromise the analysis.
The Ion Microprobe Facility in Edinburgh (EIMF) has been using Indium mounts for over
frequently used to analyse any material where low backgrounds of H and C are needed
or when any additional sample preparation would be detrimental to the work (e.g.
surface diffusion studies) or when samples can be mounted unprepared (e.g. micro-
the material has become readily available (e.g.
) in high purity (e.g.99.999%)
and at a reasonable price (~£4/g). The physical properties are listed in Table 1. Its
hardness (1.2 Mohs Scale) makes it soft enough to enable samples to be pressed into
the metal without fracturing or damage. In addition, samples can easily be recovered if
another type of analysis (e.g. FTIR) is required. The toxicity is low requiring only basic
handling precautions. A MSDS data sheet is linked below.
Hardness (Mohs Scale)
What is needed:
• Glass slide, Crystalbond or Lakeside, grinding and polishing materials. These are
used for the pre-preparation of the samples.
• Ultasonic bath, beakers, solvents (acetone, ethanol), de-ionsied water, oven.
• Hot plate (up to 200
C). Used for the melting of indium, Lakeside and
• Al-disk with blind hole for the indium metal to sit.
• Hydraulic press (~ 5 ton) for pushing the samples into the indium.
• Melinex sheet (~0.2mm thick). This is used to provide a barrier between the
hardened steel plates of the hydraulic press and the indium. It produces a smooth
surface to the Indium and prevents the indium ‘sticking’ to the hardened steel
plates of the press.
Suppliers of Materials:
1. Indium: Alfa Aesar (
2. MSDS sheet from Alfa Aesar
3. Melinex sheet: Katco, Performance Materials. (
4. Hydaulic Press: Enerpack RSM50 (
5. Lakeside: Lakeside Products (
6. Crystalbond: SPI supplies (
Dimensions in mm
Sample and sample holder dimensions
Stainless steel holder
Samples pressed into
or an epoxy resin as the embedding medium. Once ground and polished the samples
should be removed from the embedding medium, cleaned in acetone, washed with de-
ionised water, then dried. The end product should be a polished flat surface with the
samples free from their embedding medium.
Step 2: Holder Preparation Steps:
The Al-disk should be cleaned to remove any
oils or machining lubricants. The quantity of
indium required maybe calculated and then
placed in the Al-well. Indium tear-drops can
be seen in the bottom right of the picture.
Alternatively, just eye-balling the correct
needed as pressing of the sample can
displace enough indium to make the a flat
surface across the diameter of the mount.
The holder should be transferred to the hot
plate set at ~180
C and the indium allowed
Step 3: Hydraulic Press:
The indium now needs to be
sample surface is protected from
the polished steel block by a sheet
of Melinex. This ensures that the
steel block does not bond to the
surface. A 5Ton press provides
enough pressure to force the
indium into the Al-well and remove
any trapped pockets of air that
may behave as a virtual leaks.
Step 4: Sample insertion:
with a central well of indium that has a
smooth surface. At this stage small troughs
can be gouged into the indium to make room
for larger samples, so that on pressing the
indium does not flow out of the well.
Ultrasonic clean the block in Acetone.
return the holder to the hydraulic press.
Again, using the Melinex sheet compress the
samples into the indium. The photograph
shows a small fragment of a standard
pressed into the indium.
Step 5: Cleaning the sample:
Place the sample in Acetone and allow the solvent to remove any grease. Do not use
the ultrasonic bath as this dislodges the samples from the indium.
Remove the holder and wipe the surface with ethanol, de-ionised water and allow to dry.