Samples in solution can be deposited as droplets on Si wafers. Typical volume for a droplet of 2-3 mm diameter is 1 microliter. Up to 3 droplets in a row can be deposited on one 10 mm x 10 mm Si wafer. Samples that can be embedded in ultramicrotomed can also be deposited on similar Si wafers. The ideal thickness of microtomed samples is 60 nm. Silicon wafers should be cleaned with ethyl alcohol and wiped with lint-free cloth. In the figure below, ten clean 10 mm x 10 mm Si wafers are shown in a transparent plastic box. The white strip is Post-It tape, placed sticky side up. The Post-It tape has been secured with double-sided tape.

Rock or biomineral samples can be embedded in epoxy, polished down to 0.05 micron alumina grit, and coated to enhance conductivity without interfering with the measurement. The differential thickness coating method is described in De Stasio et. al. 2003 (244 kB PDF).

click for larger image

Samples are placed in the sample holder shown below, a cap is mounted on the sample surface, leaving a 7 mm diameter exposed area. The complete assembly is then inserted into three stages of vacuum chambers and analyzed at 10^-9 - 10^-10 Torr.

click for larger image Disassembled sample holder.

click for larger image Disassembled sample holder with silicon wafer.

click for larger image Assembled sample holder with silicon wafer.