Sample Requirements for SIMS Analyses Cameca ims 6f ion microprobe

There are three different sample geometries which we can accommodate: (A) 25.4 mm diameter round mounts, (B) thin-sections and (C) small polished chips. SIMS samples must be compatible with the ultra-high vacuum which is maintained by the Cameca 6f. Without a sample in our secondary ion source our instrument typically has a pressure < 4e-10 Torr in its sample chamber. When preparing samples one should avoid using materials that are prone to outgassing (e.g., epoxy). All samples which are to be analyzed must be documented in detail prior to being brought to the SIMS lab. Any sample which consists of more than a single phase must be accompanied by reflected light photomicrographs. Additional documentation may include backscattered electron images, transmitted light images and EPMA element maps. All projects requiring calibration for absolute abundances must have conducted EPMA analyses of all target domains prior to SIMS analyses. All samples must have a polished surface, and must be flat to the very edge of the sample. (If the sample has more than a few 10's of micrometers of topography we will encounter ion optic difficulties.) We can analyze only within 10 mm of the center of a sample. Please contact the GFZ SIMS lab if you have any questions.

(A) 25.4 mm diameter round mounts: Such sample mounts may be in the form of either a round thin-section or as a grain mount. Thin sections are preferred, as they generate significantly less vacuum contamination. The following picture shows both a thin-section (left) and a round acrylic grain mount (middle front). Such samples are inserted in a sample holder (front right) and the sample is held against the holder's front plate by springs (two types are shown at the rear of this photo). If required we can accommodate samples up to 11 mm in thickness, however it is preferable that samples should be kept under 8 mm in height. Sample diameter should be no less than 24 mm.

(B) thin-sections: We have constructed thin-section holders which accommodate petrographic thin-sections. Such thin-sections must be 1 inch square by 1 inch in size. The sample holders are otherwise similar to those use for the round sample mounts. Using this geometry we can measure locations that are within a 20 x 20 mm square area.

(C) small polished chips: We have designed special holders which will hold small samples without the need to imbed them in epoxy; this technique is used particularly for samples which have been synthesized for depth profiling. Both the front and back of such 'chips' must be flat and parallel to each other. An example of such a sample, which has already been gold coated, is located near the pencil point in the following photo.

The sample is pressed against the center of the face plate of a standard Cameca 9-hole sample holder using specially made springs and stainless washers (visible in photo above). Such samples can range in size between 3.5 x 3.5 mm up to 9 x 9 mm. Using this system only the central 2 x 2 mm area is available for analysis. Sample should be no higher than 4 mm tall. The advantage of this technique is that it eliminates epoxy from the sample preparation, thereby reducing sample outgassing in the vacuum.

Prior to SIMS analysis samples should be ultrasonically cleaned in high-purity ethanol and possibly in double distilled water as well.. The sample should be dried at 75C for at least 15 minutes. Samples must then be coated with an electrically conductive film prior to analysis. For most applications we employ a gold coat, though carbon and silver coats are also possible. If needed we can coat samples brought to our lab for analysis.