The Michael J. Drake
Electron Microprobe Laboratory
University of Arizona
Sample Requirements and Sample Preparation
Types of Samples
The sample must be:
- Solid and stable under high vacuum.
- Electrically conductive or coated with a thin (conductive layer of amorphous carbon. (Note we recommend that carbon coating be performed in our lab).
- Stable under the electron beam. Heating by the electron beam can damage some materials, particularly those containing a large amount of water or other volatile components which can greatly complicate analysis.
- The area of interest must be clean and exposed (i.e. not painted, varnished, covered by a cover slip, grease covered, etc.).
- For quantitative (WDS) analysis, the upper surface of the sample must be flat and highly polished (final grit size of 0.5 μm).
Sample Size and Shape
Sample size is constrained by the dimensions of our sample holders. Currently we have sample holders that can accommodate:
- Six 1" (25.4 mm) diameter cylindrical blocks, plates, or thin sections. Maximum thickness 3/4" (19 mm).
- Two 1.25" (31.75) diameter cylindrical blocks or plates. Maximum thickness 3/4" (19 mm).
- Two 1" x 1.8" (25 mm x 45 mm) standard U.S. petrographic size thin sections. Maximum thickness 0.05" (1.2 mm).
- One 2" x 3" (50 mm x 76 mm) oversized thin section. Maximum thickness 0.05" (1.2 mm).
- Irregularly shaped samples with one flat surface (e.g. polished rock slabs). Size up to a maximum length and width of 2" x 2.5" (50 mm x 65 mm). Maximum thickness 1/2" (13 mm).
Sample Preparation
Typically the simplest method of preparing a loose sample for quantitative analysis is to mount it in a 1" round epoxy mount, grind one face flat, and then polish it. For users with a small to moderate number of samples we can usually assist with this process in our sample preparation lab. Also please feel free to contact us with questions regarding mounting unusual samples.